Aha, that's it, rudestuff, thanks.
This kind of stuff would be scrutinized by Transport Canada in the case of a conversion or an application for a higher license.
Only one pilot may log PIC at a time in Canada, no matter what. If I take a PPL holder up for some hood time, I as the instructor would log PIC and the PPL holder would log dual.
(Side note - I could never really comprehend how there logically could be two PICs on board one aircraft...)