Maybe....Maybe not......I found this while watching the video posted by GM on a prototype for SEMA...
It say's wheel size
20 x 10 and
20 x 11 via Z/28 blanks...check what's written under suspension in the video.
Zoom in at
2:03 of the video below:
UPDATED 11-11-2010: Tire size up front is 285/30 R20 and rears are 295/35 R20
Screen Capture: