RE:RE:RE:RE:AIM.PR.CNo, buybacks "under par" for prefs could only happen bidding on the open stock market under very restrictive conditions (the same conditions as for buybacks of regular stock).
https://www.mltaikins.com/corporate-finance-securities/how-to-conduct-a-substantial-issuer-bid/
https://www.mltaikins.com/corporate-finance-securities/conducting-a-normal-course-issuer-bid-on-the-tsx/