Actually T12s in those EMUs are becoming quite rare, nowadays they are using T8 which have corresponding length of 1m. Most popular are chinese T8 25W tubes with very short lifespan, but I've also seen Philips and Osram T8 23W dedicated retrofit tubes and Philips T8 1m 36W which work very fine, in my opinion even better than those 23W ones. On the topic of T12s, reappearance of Polamps from 70s was a one time only event, this particular EN57 with number 1828 is the only one which received such tubes during repair in ZNTK Mińsk Mazowiecki. Most T12s in recent times were fresh imported chinese ones or from stock of Pila tubes made in Poland in the 2000s. Many EN57 have been fitted with new 18W/30W/36W transverter based lighting but those with original alternator system are still quite common. Many times in order to reduce repair costs railway companies ordered repair facilities (ZNTK) to mix old lighting with new. In such cases old alternator lighting remains predominant but in given places (most often toilets which originally had 220V tungsten bulbs powered from the same instalation as tubes) new fixtures are installed. Most often fluorescent transverter fixtures which in almost every case are wired to start at the same time as alternator lighting. Three EN57 from SKM Trójmiasto (Tricity equivalent of S-Bahn, in the beginning there were used old S-Bahn Berlin trains which were converted to be powered from overhead catenary and received fluorescent lighting: http://as.rumia.edu.pl/tt/plany/ew/ew91/91.09s.2.jpg
) have new fixtures for two 18W tubes which individually are powered by original ballasts for 25W tubes (in Poland there are no surviving working 220V 500Hz ballasts for wattages other than 25W), although those tubes are visibly underdriven. Third possible mix of old and new is the mix of old alternator based fluorescents with new LEDs.
3500K-4000K are almost exclusive in case of 25W tubes, I've seen only one 765 Sylvania so 25W tubes different than 3500K-4000K are rare. As for the effects during start here is a film which presents switch on of lighting in EN57:
Those 8W tungsten bulbs which blink once are the emergency lighting which illuminates interior in case when the alternator won't start due to malfunction, that blink is due to complicated switching of relays during startup of lighting.
Currently in Poland there are only two 4-part Görlitz double-decker sets in working condition, they are used during summertime when there is a very big increase in the amount of people travelling to Hel sea resort. Those sets (sometimes with additional solo double-deck Görlitz railcar from 1988 or 1989) are used on Gdynia-Hel railway line as a regional train, one in extended relation Chojnice-Gdynia-Hel. For years there've been talk about finally sending them to scrapyard, but due to underperformance of new DMUs they are still present on that line and at least in 2017 they should be seen again, though 2018 isn't sure, it is possible that 2017 will be their final year. Originally those sets had 25W tubes like those made for Deutsche Reichsbahn, but many years ago lighting was converted to transverter based with transistor transverters for two 20W tubes in series. Old fluorescent fixtures were retained (tungsten bulbs fixtures were changed to polish made), only lampholders were moved closer to each other in order to fit to shorter 20W tubes and as two tubes are connected in series, only every second fixture has gear installed with wires going between fixtures. If I remember correctly STOK2 transverters were used, here is schematic of such transverter: http://www.zeus.krb.com.pl/?przeglad-rozwiazan-ukladow-i-zespolow-elektrycznych-oraz-elektronicznych.-czesc-i,28
I have photos of interior of those Görlitz sets with lighting on, I will upload them in some time.