Yes, Lexus uses the Potenza, I have it on my IS.
RE92 sucks, it came with my 96 Eclipse GSX, and its traction is not that good and the tread worn off at around 11000 miles. I switched to Dunlop SP8000 and had that until I sold my car.
The 17" wheels come with Bridgestone Potenza RE040 _OR_ Goodyear Eagle GS-D. The factory just uses whatever they happen to have available at the time. Supposedly 66% are Goodyears and 33% are Bridgestone.
The sales person also informed me that they will store my summer tires. Didn't mention anything about offering winter tires for $50 though. I didn't inquire any further since it's the middle of summer and I don't want to be thinking of driving my IS in the snow yet.
But now that we've brought it up...anyone have any suggestions for a good all-season or fall/winter tire (besides Blizzaks)?