I can conclusively say that one can enter Canada using COPR and Passport without the PR Card after completing landing formalities as I just did that a week ago at Peace Bridge and also entered back into US couple of days later at Rainbow bridge using AVR. My PR cards were delivered at a friend's address and I didnt want to take a risk to courier them outside of Canada so that I can obtain them. I flew to BUF and then rented car to go to GTA Area to personally collect the PR cards. At Peace Bridge, CBSA officer just asked how long I'll be in Canada for and where I reside, I was truthful and told I'll be in Canada only for a day or two and will return back to US. He was okay with it and just looked at Passport and COPR and let me go. Upon return similar thing happened at rainbow bridge, I handed CBP officer the I-797 and passport with expired H1B visa and he simply looked at it, asked how long I was in Canada for and asked where I'm heading. Since I live in CA, I told him I'll be going to CA after dropping car back at BUF airport and he wished me good luck and let me go. All it took was about 30 seconds and that was it. Good luck to anyone who wish to cross border with COPR and Passport, it surely works.