Originally Posted by
yyz_atc_qq
T+ does offer free same-day standby for Rapidair even if connecting further on, BUT.... only the itinerary is a domestic/transborder. If the itinerary is true international, then NO free same-day standby even for Rapidair flights.
Not sure OP's itinerary as s/he rang YOW concierge in the good case.
I made the comment because AC1109 routing is YHZ-YUL-YWG and AC655 is YYT-YHZ-YUL. The common segment is YHZ-YUL. So it's not a Rapidair flight. S/he could probably have requested a same day change, subject to the applicable fee if seat was available for sale on the AC655, and then request to be put on the upgrade waitlist.
As OP was also talking about upgrade window, I assume that s/he's on a Tango Plus fare.