Cedilot has been proposing that theory for years. Back in 2010 he said the same, while we now know that the take-over came from groups within Montreal. I don't believe the Montreal Mafia, which comprises hundreds of associates, will allow Ontario to rule over them. The arguments that are now made against Bonanno influence also apply for Ontario.
I agree with you back in 2010 they were saying the same thing because the Rizzuto clan were dealt with heavy casualties but things started to change in Rizzuto's favor when he was released in 2012. His rivals were dealt with heavy losses too. But now since 2015, the Rizzuto clan are being attacked once again but I do not see much retaliation. So there maybe some truth in what Cedilot is now saying. It is just my impression of things.