Say you got your AOR 3 weeks before your work permit expires. You send off an open bridge work permit application 2-3 weeks before, what happens? I heard it takes about 45 days to process so do they say they can't process since you sent it off too late or even if your work permit expires and your out of the country is it still processed and you can return?
As long as your application is received before the expiration of your old work permit, it will be considered "on time." It will continue processing; after your old work permit expires, you will be on "implied status" as long as you remain in Canada. This means you can continue living and working in Canada under the same conditions as your old work permit, until you receive a response to your BOWP application.
If you leave Canada during that time, you will loose implied status. Since you have to be living in Canada to be eligible for the BOWP, I don't know what impact (if any) that would have. So I would suggest that you stay in Canada until your BOWP has finished processing.