What are my chances if I book a M fare from LHR->YUL return of being able to upgrade at the 4-day *E window? I have no idea how hard it is to upgrade this flight. I'm looking at doing this March 25 -> April 5 (+/- a day either way).

I also have to fly from DUB->SFO next month, April 11->25. Am I crazy to fly DUB -> LHR -> YYZ or YYC or YUL -> SFO? Just to cross my fingers and get upgraded? I could get any number of one-stop flights but would never get upgraded on any of them. Is my best bet for getting upgraded on this to go via YYC? Or YYZ? Or some other less common gateway?