Here is a little outline taken from different news clips and authors of mafia books.

-2009 Salvatore Montagna was deported to Canada.
- The feud against the Rizzuto's had begun years before Montagna's return to Montreal.
-Upon his return Sal made trips to Hamilton and Toronto with the objective to gain backing from Calabrian clans.
-While in Montreal he managed to form an alliance with the Arcuri clan and other Montreal clans such as Mirarchi/Desjardins, DeVito & others who were out of favor with the Rizzuto's.
-Dec.2009- Feb.2011 During this time, under this newly formed alliance, things started to happen at a rapid pace & high level targets from the Rizzuto clan were being murdered.
-Sept 2011 Sal Montagna later became overzealous,started to raise dues and pushing his weight around against some of the people (Desjardins) he had aligned himself with.
- Sept 16, 2011 An attempt was made on Desjardins life, and soon after the alliance quickly dissolved but the Arcuri's remained loyal to Montagna.
- Oct. 25,2011 Mirarchi (associate of desjardins) made a trip to Toronto .
-Next months ahead people from Arcuri's crew including Montagna were being killed.
- Oct 2012 Vito Rizzuto got out of jail and people opposed to him were being killed until he died in Dec. 2013. The war to this present day hasn't stopped

The Bonnano's may have played a role but there is no evidence to support it. It is unsure whether Sal Montagna planned this in New York prior to being deported or whether he decided this on his own.
I stopped the outline at 2011. When Vito Rizzuto got out of jail in Oct 2012, people opposed to him started to drop off until he died in Dec. 2013.