The Holden Monaro is called the GTO in the US. As far as I know the 2010 Camaro is a "fresh start." It does not share a platform with any other vehicle in Chevy's lineup.
It is loosely based on the Pontiac G8 platform, but has been changed up enough to be considered it's own. The G8 is on the Zeta platform (which was designed by Holden), and they say that the Camaro would justify calling it the Zeta II.
As a side note, the V8 Camaro is estimated to top out at 4,000 lbs, which will be very close to the Challenger RT (SRT is about 130 lbs heavier), so for those that think the Challenger is a pig, the Camaro is not far behind it.