Well, this problem is not in the fixtures, but somewhere in the street wiring...
They have replaced the fixtures, but either the workers did very lousy job there (bad connection may happen, but don't tell me, they were not able to see and fix it before leaving the "scene", if they would do the required inspection after the installation properly), or it was the complete installation, what needs complete overhaul...

Being a joker here-if they aren't going to fix these lights----Get out the Donna Summer records,Bee Gees records and hang a disco ball under each light--INSTANT DISCO STREET PARTY!!!So sad Detroit spent all that money on these things--only to be rewarded with lights that don't work.At least the older HPS lights WORKED!!!!And didn't put out distracting flashing and glare!And--to top it off the probably don't have the money to replace these again.Is there some sort of warrantee with these lights that can be worked out with their manufactuerer?

Anyone swapping the soundrack on the news videos with "The Power of One" ?

In the video they say the older lights didnt work. I can expect that, after they didnt relamp for yeas and let all the lamps go EOL..... Maybe some ignitors/ballasts were damaged too

In this specific road possibly there was quite extensive damage to all old gear if the Neutral opened with the HPS lights before, then temporarily came beck in contact when they disturbed it somewhere during the LED replacement, and now loast contact again

So it might be up to more than just lamps, but otherwise yep replace it with HPS and get good lighting for years

When the lighting didn't worked before, it means it was the wiring installation fault. So that means lousy inspection/diagnostic work before they decided to switch to these LED's...
Even with old, deteriorated gear and old lamp it is very unlikely all failing at once, so once someone would even try to power the old installation up and observe it working for some hour, it should have been clear there is much more to overhaul than just the fixtures...

But I may imagine how that may have worked at the city hall:
The lights didn't worked, it was clear it would need some significant work, so the officials called some lighting companies to asses the situation and bid for the solution.
And one of the companies wanted to sell the high margin LED's, so claimed the lantern replacement for shiny LED's would fix it all. Obviously with just replacing the lanterns, they may have offered the lowest price, added the babbling about low energy use and so on, so won the auction.
And if they prepared the contract so it stated just "replacement of the fixtures", the company just replaced the fixtures and said "Good Bye, contract done". The lights do not work? "Sorry, the lanterns are OK, it is the wiring, the contract ordered just the lanterns"...

It sounds very much like the department in charge of streetlighting just wanted to give the job of fixing the problem to the company who could talk the best eco babble waisting thousands of dollars just to be green. Instead of paying a real engineer to fix the old lights and find the broken neutral cable
Sounds like local authority everywhere

In the othe vide (where the LEDs are working intact, on another road in the same city) they mention that lights are out except a last working one, then mention it cycling, then going out

That shows that while in this road the problem is Neutral, in other roads (that got the LEDs too) it was just no maintenance for years...... And possibly vandalism too

Bad connections, this is simply.

Makes good sense the main neutral lead has a fault since all of the lights are affected-the linemen have a job to do-repair the faulty neutral line!Then the area should have streetlights instead of disco lights.Its kinda like a radio station I tried to help out--they buy a new AM transmitter when their antenna ground system is bad-like over 40 yrs old.A new transmitter isn't going to fix this esp when all the readings of their system don't match their orig licensed specs.someone thought new lights were going to fix an OLD problem.The radio station will have top plow a new ground system to fix their problems.

Seems like all these major cities have SLS... Shiny Light Syndrome.  A GE M250r2 or M400r3 would be cheaper to buy, and the cost savings negligent.  Tried and True is always better.  Seems to me like LEDs are here to stay, but I think they are rolling them out too quickly.

We had the same with the LED lamps at my hostel yesterday: http://www.lighting-gallery.net/gallery/displayimage.php?pos=-125504 because of low mains voltage. I'm guessing that this was the same problem at Detroit streetlighting electric infrastructure as well.