I seriously doubt Desjardins has any worries about repercussions for killing Montagna other than from the Mounties. The Bonanno's are not after him, it's the Sicilian's in Montreal that he will have to worry about. Mirarchi is his only shot at living. But him killing a made member doesn't mean shit in Montreal anymore unless the guy was a Rizzuto or Ndrangheta.
As for his sentencing, I don't know Canada's laws but I wonder if he gets out of that plea agreement since the evidence couldn't be used. I don't think I've seen a case like that before.
Agreed that he has more to worry about the old Rizzuto group in Montreal than the Bonannos in New York. Other than putting a contract on him, of which there is anecdotal evidence, I doubt the Bonannos are inclined to send anyone over, but they don't need to either given the fact that Desjardins already has enemies over there looking to kill him. I think he still is, and will remain, a high priority target in Montreal.
You can't leave out the Arcuri's, they have always been loyal to the Bonanno's. Everytime there is a conflict they come out of obscurity and become part of an alliance.