The GM Utility Bars appear to be identical in dimensions and style to Thule bars and may well be made by them so any Thule accessories fit them. We got ours at:
http://pontiac.dealerfit.com/s...8.phpThey attach/detach easily and come with locks.I'd expect the Thule Criterium bike mount to interfere with the hatch opening. Might be better to go with a fork-mount and put the bikes on facing the rear so there's no overhang past the rear crossbar. That would require front wheel removal, but that's usually pretty easy.