Man I wish someone high up in the Montreal faction would flip so we could get some concrete information on what happened to the Bonanno-Montreal relationship, when exactly it split and why. I think we have a fairly good picture, but much of it seems based on speculative possibilities.

To me it seems as though the seams began to split as soon as the Rizzutos took over but didn't come completely apart until just before the Sciascia hit and was possibly the catalyst for said hit. Wikipedia, citing "the sixth family", claims that Sciascia kept taking Rizzuto's side in disagreements with Massino and began acting more independently, making him a possible threat to Massino's leadership.