I (a Canadian citizen) used a positive PCR test taken 1 month prior to board a flight in late November from IST-YYZ. It was shown at gate check-in, then a secondary inspector whom I had to convince with wording from both the Turkish Airlines and Transport Canada site, then to another agent at boarding who had to "phone upstairs" for an OK. It was eventually confirmed that I was OK to fly. This is just the airline covering their butt to avoid fines.

CBSA didn't look at the test result. In ArriveCAN there was simply a question whether you had a positive PCR test from 14 days+ before, but didn't have to upload anything. I was not ordered to quarantine at the border and did not have to take an arrival or day 8 test, but things have changed a lot since then.