From what i am reading, you can apply 4 months before your work permit expires.this is as long as your application for PR is on the process. My brother in-law's WP is going to expire this june 2013 and CEM has requested for remedical for his family because the first one has expired. Now we are worried if 3 months is enough to process his papers. Bridging is one of his options if the company he's working will not sign another contract.