I'm assuming Direct TV functions the same way for NHL Center Ice as for me on DISH.
You say you follow Montreal but you don't say if you LIVE in the Montreal area. If you live in the Montreal area, you have to watch your games on your RSN - Rogers or whoever is your local regional sports station.
For the sake of argument, let's assume you live in Arizona. In this case, you will receive all Montreal games on NHL Center Ice with the following exceptions:
If a Montreal game is the primary broadcast on NHL Network (and they are not playing the Coyotes), you would watch the game on NHL Network. Likewise, if the game is telecast on NBC Sports Network or NBC Network, you would watch the game there.
Here's where the blackout rules can get a bit tricky.
If (you are in the Phoenix area) and Montreal is playing the Coyotes and the Arizona RSN is broadcasting the game - you would watch it on your Arizona RSN and it doesn't even show up in the on screen guide (with DISH anyway). On the other hand, if NHL Network or NBC Sports Network does not have the EXCLUSIVE rights for that Arizona-Montreal game, the game would be blacked out on NHLN or NBCSN and you WOULD get the game on NHL Center Ice.
NHL Center Ice will give you all regular season games and first round of the playoffs. One we get to round 2 of the playoffs, NBC has the rights for all the games. Since there are so many games in round 2, some will be on CNBC, NBCSN and other NBC affiliates.
As for choosing the Montreal or Arizona feed, DISH will sometimes offer both (this season), most often not. If you DO get both feeds, they should be listed separately in your on screen guide.
Hope this helps clear things up a bit for you.