Not sure if this helps, but just because your PR card expired doesn't mean you are no longer a Permanent Resident. Your status in Canada is still a "Permanent Resident". It is exactly like the case of a passport, just because your passport expired doesn't mean you are no longer a citizen of that country. PR card is only a document. Your status will remain a Permanent Resident and therefore you are legally authorized to work in Canada. Many workplaces require your SIN card number and from that they can determine your status. I believe the first three digits of the SIN card tell whether you are a Permanent Resident or a foreign worker, but I might be wrong(not too sure of that). Your SIN card is active for 99 years or so. Hence, if you haven't voluntarily renounced your PR status, you still continue to be a permanent resident and can work anywhere in Canada.