I agree, we could say that the real thing that broke the chain was the killing of George from Canada. That was the last thing, and the Rizzutos were looking for a reason to say "Fuck you New York". And thats what they did with the killing of Georgie.
What's interesting though is, Vito Rizzuto reportedly sent the message to NY that he didn't recognize Montagna as his boss. If the ties were completely severed with the murder of Sciascia years before, one wonders why Rizzuto would need to say that at all.
In that case, we could assume that they still recognized the Bonannos as their leader and still kicked up money. So that makes them a crew of the Bonannos, not a independant family like most people think. But if so, the shit thats happening there is still a Bonanno issue, if they are a crew and still tied to them, they wouldnt let those things happen. So its 2 possibilities, Bonannos still trying to maintain control, or they simply say: fuck it, its Canadian business.
