I doubt they will let you enter. You will be flagged and immigration will be highly suspicious that you do not have a return ticket.
To be honest, I too, am highly suspicious. Why don't you have a return ticket? Are you planning to arrive in Canada and disappear?
I left Canada January 2011 - purchased a return ticket back home, it was cheaper to buy a return then to travel back home on a one way. This ticket was purchased when i withdrew my refugee claim, now i have the second portion of the ticket...a ticket back to Canada. I was going to use that part of the original ticket, come back to visit...stay and visit family and friends and then buy a ticket home...figured that it will be summer and i can look for a charter flight back home.