I wrote a mail through web form on IRCC asking where was my passport. After two weeks, they responded to me. They told me it was supposed to get it when I receive my PR card, but if I wanted it before, I will have to contact the office that had my passport. In my case, they told me that my passport was on 6900 Airport road. I went directly to that office and brought the CopR document, driver's license and a formal letter that said: I would like to get my passport back because I already got a permanent residence. I did not give any explanation, but it is up to you to write the reason you want it back.
They accepted my letter without a problem. Two days after they called me to pick up my passport. I went there, waited for a while, signed a form they gave me and that is all. I got my passport back. There were no questions nor issues with that requeriment.