You can only take up a PDF at a Canadian university or government research group if you're PhD is awarded at a foreign university:
You may hold a Postdoctoral Fellowship abroad only if you have received (or expect to receive before you take up the fellowship) your doctorate from a Canadian university. You are not permitted to hold your fellowship at the same university (or its affiliated hospitals, research centres and other laboratories) where you received your doctorate. However, you may request an exception that will be considered by the selection committee. The request must be based on family reasons (e.g., a spouse's career) or scientific reasons (e.g., availability of specialized equipment), which make it extremely difficult for you to leave a particular university. You must change department and supervisor, or change university if there are two in the same city. Given that NSERC may not approve your request for an exception, you are encouraged to include an alternate location for your Postdoctoral Fellowship. You may not hold the Postdoctoral Fellowship with your PhD supervisor, even if your supervisor changes research institutions.
This can be found here: http://www.nserc-crsng.gc.ca/Students-Etudiants/PD-NP/PDF-BP_eng.asp
