Whether this war is internal or not, if they are smart they should stop. All they are doing is weakening themselves to the point that the HA will be there to pick up the pieces. I came across a book that I bought called " The Road to Hell" print 2003. The book is about the Hells conquering Canada. There is a passage revealed by an informant working for the Hells that Mom Boucher wanted to wage a war with the Italians after they were done fighting with the Rock Machine. If true it goes to show you what their objectives were back then. Will the Cazzetta's and their cronies aspire to the same objective is something to think about ? Moms idea was to eliminate competition in the drug trade and the Italians, according to him, were their biggest competitors. He went as far as sending someone to film people going in and out of a Cotroni funeral.
It's interesting and I think the Hells have the manpower to do it. However, the Italians in Montreal have connections all over the world. Politically and economically they are far more powerful than the bikers. The Italian Mafias control a large chunk of the global drug trade and they have very good relationships with the South American cartels and other suppliers. If the bikers annihilate the Mafia in Montreal who wants to do business with them? Not to mention the potential vendettas from the Mafia's associates and vast families. This is a fantasy that you'll only see happening in Marvel comics.
You make an interesting point also. All I am saying is that there is another enemy the Montreal mafia has to worry about.