Local shop is selling out it's stock of Megaman 12v dc cfls for half price and that reminded me about this question. I've been using these CFL's for a long time at my familys summer house. These have been pretty reliable to start even in winter time. Now I still have some old one's left from when I bought the first's around ten or eight years ago and those first one's I got have preheat-like starting and you hear something like glow starter operating when you flip on the electricity. Newer ones all have rapid start like starting (I think Medved once told that it's a common method on low voltage fl lamps) I was just wondering could these older ones really have glow starter inside and what kind of ballast circuitry those could have? I dont want to tear open a working lamp but when one of those will fail I probably cant resist my curiosity.

If I remember correctly those early one's I had use to have some realiability problem and some of them did not last long. I've been moving slowly towards 12V LEDs but only in recent years those have evolved so good that you can use them to replace those cfl's. I still have some low voltage incandescent in use at areas like cellar or storage shed. Also some 18W fluorescent fixtures that have been converted to 12V DC.

Quite frequent designs use just relays with an electronic timer for the preheat, I would guess the "click" comes from there.
The rest of the ballast was then just a common Royer oscillator style ballast.

I would expect some newer ones will use some kind of frequency controlled programmed start ballast or so, mainly once the IC's like IR2153 or similar and mainly the very low RdsOn MOSFET's became available for cheap...

I thought about that too but if there is a timer it's time is really short. If you know how those safety starters like osram ST171 start's it's pretty similar to that. starting with many short flashes and you hear that click (what sounds to me as bi-metal click) sound many times until the lamp finally stays on. I could try to take a video when I visit there next time.

Well, even when I haven't seen any, it is well possible for some designs to really employ the glowbottle...

The "safety" starters are no different from any other glowbottles, of course until the cut out switch activates...