yes as long as it will be valid by the time you going to enter Canada again through land border, so once you enter Canada through land border just show them a print of your ECOPR, your passport visa and if they ask you where is your PR Card then just tell them that you haven't received it yet.
Apologies, I have two more questions:
1. If I am flying to the US and then entering Canada via a land border, will the US inquire about my legal status in Canada? If they do, should I present my COPR or my visa stamp along with my work permit?
2. If I leave Canada after receiving my COPR, will my PR card still be delivered to my Canadian address while I am away?