If you haven't seen this elsewhere GM now has an "official" fix for the creaking roof issue, new parts need to be ordered.... these are the 2 pins at the front which anchor the top to the car and the strikers are the assemblies which you swing sideways to lock the roof in. Apparently some changes to the design have fixed the noise issue. These are taken from a U.S GM Service Bulletin, document ID 4277613 issued Oct 2nd. It states that it applies to export vehicles as well which I assume means Canada.
Parts are Left Striker - # 23374302 Right Striker = # 23374303 and 2 Pin Assy - # 23412818
Parts are Left Striker - # 23374302 Right Striker = # 23374303 and 2 Pin Assy - # 23412818