I agree with Medved on this . All of the fixtures you've mentioned are no longer available new with exception of the OVHs . I'd say the utility is replacing everything for standardization purposes with the intent of limiting replacement parts requirements for multiple fixture brands . 
 
 Now , will they convert to LED at some point in the near future ?? Probably !!  It all depends on how much of a financial incentive they are given by the either the feds or possibly a lighting company and when .  If the someone comes in and offers them some major incentive to "upgrade" to LED , they're gonna take it !!   

Just a quick update, things have really gotten way out of hand. Hundreds of more fixtures, M-400s, M-250R2s, Series 25s, OV-15 Tudors, and others got replaced by those dumb Cooper OVHs in the past week! It’s almost like they’re putting in a new lighting system citywide. I’ve been concerned about the LED upgrades, but now it’s something else. It’s only a matter of time before they get trashed then replaced by LEDs.

Unfortunate, but I don't think they'll trash the OVHs if they get taken down very soon. They'll likely reuse them in a place that still has HPS and has no current plans to change them.

Just a quick update, things have really gotten way out of hand. Hundreds of more fixtures, M-400s, M-250R2s, Series 25s, OV-15 Tudors, and others got replaced by those dumb Cooper OVHs in the past week! It’s almost like they’re putting in a new lighting system citywide. I’ve been concerned about the LED upgrades, but now it’s something else. It’s only a matter of time before they get trashed then replaced by LEDs.

So dumb, they’re going to be replaced by LED anyway! And it’s even worse how some of the older lights still worked!

Pretty much everything got replaced here. There are still (literally) a handful of HPS fittings I know about, but apart from that, everything is gone, to be replaced by... 

There was no need for it; spot replacing broken or EOL lamps I can understand, but global replacement of EVERYTHING, whether it's working or not, is something I will never understand 

Over here it was common for a utility to standardize on a couple luminaire models, usually one small model and one medium and then use that model for all new installations and spot replacements whenever an older luminaire was damaged. Anything requiring more than a lamp or PC replacement, they'll swap the luminaire out. Older luminaires got to stay as long as they still functioned, there are still some 1960s era 1st gen OV25s and GE M-400s in use. In some very rare cases, possibly with a lot of failures on the same street will they opt to switch out the whole row of luminaires.

In my area they standardized on the Cooper OVF and American Electric 115 FCO. In Toronto they standardized on the American Electric 115 and 125 drop lens for HPS cobraheads and the King Luminaire K215 for MH gumball/teardrop installs.

Occasionally a different model will be installed, typically by a contractor as part of another project. 

Did anybody realize that they might be putting in the new OVHs to "up" the lux on the ground to original values or what's in the books?

Way back in the MV & incandescent era, mass re-lamping was common. This was mainly to maintain the required lux, otherwise it was deemed unsafe and/or uneconomical to run.

Regardless of the potential reasons on why they are installing OVHs, they’re all guaranteed going to get replaced by LEDs eventually.

Standardization of the HPS components seems pointless, especially if the fixtures are only going to be in use for a few months. It can’t be mass re-lamping because SCE doesn’t do that unless it’s a pole replacement project, which they’ve already done in the city years ago. Unless I talk to a SCE crew about it, there’s no clear answer yet, but the OVHs still suck.

All the city has to do is sign up for SCE’s SL-3 program, approve it, then bam! LEDs would be installed in a matter of weeks.

Here back in the 80s, our street lighting was maintained by Congleton Borough Council, and they were pretty efficient with not wasting money on street lighting, back then there was no such thing as PFI schemes and repairs were only done when needed.
I remember them fitting Metrovick SO-50s once to replace damaged lanterns, (at the time I thought the SO-50 was a new lantern), as I’d never seen them before anywhere!, I only found out years and years later that they were actually a 1950s lantern!!!
But I thought it was cool of CBC to have kept a stock of these 30 years later, and use them for replacement purposes! 

Yeah my utility hasn't been interested in any standardization of fixtures. It seems like old fixtures mostly get left unless they get a report on it, and even then, sometimes they do nothing. There are plenty of MV lights still in use, even if they are dimmed out or dayburning for years.

Even with the switch to LED, they haven't seen interest in using the same models, first it was ATB2 and ATB0, no rhyme or reason to where or why, then ATBS showed up, now they seem keen on using ATB Micros everywhere. The only common factor is they're all AEL! And when they first started using the ATB2 and ATB0 they were equally likely to install a 115 in HPS instead of an LED.

Same here after the move to LED. There are around 4-5 different families of LED luminaires in use here. Also interesting to read about the case of the council keeping a stock of luminaires for replacement to last 30 years.

No idea what they use here, all I know is they're ugly glare bombs 

Same here after the move to LED. There are around 4-5 different families of LED luminaires in use here. Also interesting to read about the case of the council keeping a stock of luminaires for replacement to last 30 years.

Street lighting was more simple here back in the 70s and 80s, whatever council you were under did the lighting!, we were under Congleton Borough, the neighbouring town was Vale Royal, and larger work such as motorway and main A roads usually by contractors David Liningtons.
Now we’re under Cheshire East, with Vale Royal becoming Weaver Vale!!, (who don’t even have a street lighting department anymore)!
Cheshire East do have, (or did), have their own street lighting department, but there’s another contractor called Ringways now, who’s bucket vans you tend to see out more doing street lighting! It’s all very confusing now to what it used to be?

We never see anyone doing it here, they sneak in under cover of darkness, or that's how it seems 

The HPS post tops outside our kitchen window got replaced at what must have been stupid o'clock in the morning; we went to bed at midnight with them lighting up the area perfectly. Then when I got up for a pee at 6am, I looked out of the window and nearly had heart failure, they were all GONE 

A couple of years or so before that, they took advantage of our being away for two weeks to do the same to all the (perfectly working) HPS lamps in the main street 

That’s really unusual for street lighting repairs to be done between 12 and 6!  , I’ve never heard of this here?
Street lighting was definitely better off under local councils, as they didn’t tend to waste stuff, these massive contractors today just seem to be given a blank cheque from the government!

Street lighting was definitely better off under local councils, as they didn’t tend to waste stuff, these massive contractors today just seem to be given a blank cheque from the government!

Well said, over here some cities even rebuilt luminaires in house. There's still some old 1960s era MV luminaires that got a new lease on life in the 80s and 90s. They got taken down, a new coat of paint and a rebuild to HPS and then reinstalled. Now they just replace if it need anything more than a new lamp or photocell.

We never see anyone doing it here, they sneak in under cover of darkness, or that's how it seems 

Yeah I never spotted any of the crews here either, I heard they do sometimes work at night to make it easier to spot any failed units. Over here they replaced the lights on my street during the day. When I left in the morning it was still HPS but when I returned in the evening, everything got LEDized.