The only "special tool" needed for diagnostics of these newer vehicles (listed below) is the GM MDI (Multiple Diagnostic Interface)($999.95). which was introduced in the fall of 2007 for pass-thru programming.
The new system is called the GDS (Global Diagnostic Systems)
GDS is required for diagnostics on the 2010 Chevrolet Camaro, Chevrolet Equinox, Cadillac SRX, Buick LaCrosse/Allure, and GMC Terrain. It is not a "tool" that needs to be purchased it is a computer program that interfaces with the MDI.
Any dealership claiming they "can't" work on it because they don't have a diagnostics tool (MDI released in 2007) Is not a dealer that would ever see me in their doorway. Technology going into vehicles now'a'days far surpasses anything in the past. Any dealer not keeping up with the times is not someone that I would feel qualifies to work on any newer vehicle.