I disagree with your the premise, "had Vito never been imprisoned".
Same thing could be said with Paolo Violi who was also imprisoned when the Rizzuto clan made their moves. Frank Cotroni was also imprisoned.
The difference between now and then is that the Vic Cotroni was probably given orders by New York to stand down or he decided he had enough and decided to retire. The difference now is that they do not answer to New York and several capo's from the Cotroni clan decided to strike Rizzuto while he was vulnerable in jail. Furthermore in 2001 Paolo Gervasi wanted to revenge his son's death, he sent two contract killers ready to kill Vito and two of his associates and the attempt was foiled because of police intervention. Again someone could say things would have been different had they succeeded. I believe that fate sometimes plays a good part in determining events.
I also do not dismiss that fact that Ontario may have played a role to destabilize and eventually take control of the Montreal drug trade.