Well, we're making this up as we go along but you could see Air Canada ticketing at the airport and explain that you've got the visa to get aboard the jet, but are concerned about the ARC and instead of having an issue after a long flight could they contact their Canadian Liaison Officer and confirm that you've received the ARC in their system.
It's the simple truth that the visa office is very hard to contact and since they have a direct line of contact, and you'd like to be tan Air Canada passenger - why not?
The Liaison should be able to settle it one way or another, but I only offer this because issuing the visa without an accompanying ARC can't be the process because how could the airline possibly know about the requirement for an ARC? They see a visa and say welcome aboard.
Will it work? I don't know, but the Canadian public servant who's paid to work in the High Commission and routinely talks to Air Canada is pretty much there for this sort of purpose.
Air Canada should ask, "please confirm if we can board this person with a visa, but without a physical ARC? Please confirm their ability to lawfully enter Canada?"
I'm sorry if it doesn't work but perhaps it may.
