Initial PR card - pick up notification.

[Rob_TO]

I have heard that a PO box would be acceptable so you may ask about that when you land and once you are in Canada and have arranged your PO box, mail forwarding, whatever, you can inform CIC of your address.

Be cautious around this: http://www.cic.gc.ca/english/resources/manuals/bulletins/2013/ob491.asp

As PR Cards are not mailed to P.O. boxes, clients who indicate a P.O. box instead of a mailing address will have to provide justification as to the reason they do not have an acceptable mailing address

There is info here around using a representative to receive PR card, but the part I bolded seems to be a generic rule for PR cards in general. Even if CBSA accepts the address, when CPC-S actually processes it there may or may not be an issue in using a PO Box.