It depends on your passport. Airlines have a reference called 'TIMATIC' which will tell them visa and ticketing requirements according to passport presented.
For example, as a British Passport holder, you do not need a visa for travel, but you would need to present a return ticket, UNLESS you have provide proof of status in Canada ie: work permit, study permit, PR card...if the airline was to send you and you were to be refused entry, the airline is liable for hefty penalty charges, which is why they care. Your issue would be with the airline letting you travel on a 1 way ticket in the first instance.
I worked for a major airline for over 15 years and if I had a check in agent who had a passenger present themselves for check in with a one way ticket, without the proof that they would be allowed into Canada and without a return ticket.... I would have refused that passenger travel.
I would get a copy of your COPR sent to you, I would have accepted that, had I been shown that... but that's down to my discretion as it would not be the actual physical legal document in my hand.
To be sure, I would advise purchasing a fully refundable ticket back, and then cash it in, when you are here.