I hope one of the professionals can help me with this one.

I just bought 5 SDW-TG 50w's at the thrift shop for 1 euro a piece. But now i'm running into the problem of drivers being effectively unavailable. I found one at Solidlight and e-mailed them about the availability but i expect a 'Sorry, we don't have them anymore' like i had with SBMV's and even halogen spot lights - after i ordered and paid. EDIT: they indeed don't have any in stock.

I already have an electronic 50w SON driver. A son 50w is rated at 52,5w 85v, the SDW-TG at 54w and 84v. Extremely close. Does anyone know if this will work without damage to either the driver or the lamps?

I also have an SDW-TG 100w driver. The datasheet says 'for 50 and 100w' but i cannot believe that. The label on the driver only says 100w, and i think the datasheet means that the driver is available for 50w and 100w lamps.
If anyone would like to trade the 100w driver for a 50w one, let me know! Keep in ind SDW-T and TG are not the same.

Those specs are very very close, however I believe white SON lamps have much higher tolerance in terms of voltage and current than "normal" SON. I believe the only thing this affects is the lamp color though.

So as long as you aren't running all 5 of them at once and want them to all look the same exact color, you should probably be fine, but I would wait for someone else to respond to this because I could be wrong.

Yes I can confirm 50W SDW-TG lamps work okay on 50W metal halide electronic ballast. HID-PV C 50W IS CDM by Philips in my case. Some caveats:

While a new SDW lamp has working parameters close to that of 50W HPS(euro)/MH, as the lamp ages it needs to be run at reduced power to stay at it sweet 'golden light' spot.

Nitrogen-filled compact SDW-TG seems to be a bit less fussy about this than older vacuum SDW-T.

I tried only moderately used lamps.

SDW TRIAC controllers for magnetic ballasts are of course personalized for each wattage of SDW lamps.
 

I tried it out on my Philips Primavision SON-CDO 50 driver. It appears to run completely fine, though i turned it off after 20 minutes. My phone recognizes the color temperature as 2500k so it is well within the ballpark.
No clue how it will behave later in its life, but i'm very happy and will be mounting the lamp socket in a 'nice' lamp to enjoy the beautiful 'White SON' light every night!

I've seen Philips SDW-T working on HPS/MH magnetic gears, in supermarkets, and they have poor colour stability. Some where 2300K some 2700K and some even 3200K.
What happens to old SDW-TG lamps on HPS electronic ballast? Are they simply red out like regular HPS?

I have no clue. We'll know in about 8000 hours i guess