I'm a recent temporary newcomer to Quebec doing a large implementation of an information system. It appears that most people in western Canada without much knowledge of Quebec seem to use the PQ abbreviation...myself included until I came here. This despite Canada Post's recommendation. Almost ever Quebec resident I've had this discussion with seems to raise their eyebrows at the PQ abbreviation as if it has never existed. Anyway, it would seem QC is the preferred abbreviation of Quebecers and the gov'ts. Our software now uses both abbreviations.