As for 120.425, it was found during a routine band scan and shows up with a ? on this page:
Okay after further checking I see it is a new Montreal Terminal (Departure) frequency. The same info. I have also lists 118.075 as a new Departure frequency as well. These 2 new frequencies were added as part of a Montreal Terminal Airspace redesign back in March of 2013.
Also on the Center feed you have 132.55 listed. I haven't listened to that area in depth recently but from what I recall it seems (?) they have stopped using 132.55 and replaced it with just 132.350 (merged the sectors permanetly ?). From what I've heard so far it doesn't appear you are hearing the controller in that sector ?
As far as I can tell so far the only Center controller you are able to hear on the Center feed is on 135.600. This frequency appears to be cross-coupled at all times with 128.775 (Ottawa - south area), 126.575 (Mount Laurier - north area), and 133.900 (YFJ area).
From what I've heard so far this is what I think you should cover on the Montreal Center (low) feed.
120.425 should be removed and added to the Terminal radio
And if you get a dedicated Montreal Center (High) feed.
134.400 (covers 127.875)
133.225 and 123.925 are almost always cross-coupled into one sector, but you wont get the controllers in Monteral. During the overnight hours all sectors are combined and would be heard on 134.400 (cross-coupled).