Baseline is from the Toyota Avensis (European Toyota)
Drivetrain from the Camry
Same stock tires as the IS300 (Toyota Altezza (Japan))
The xA and xB are Toyotas in Japan (Toyota Cube for the xB, I'm not sure of the name for the xA).
FYI... Toyota Motor Corp. USA has discontinued the Celica for the US market. I believe the tC is to replace it's spot. Perhaps they will release the Supra now. Nissan and Mazda already have the market claimed with their 350Z and RX-8 respectively.