When I took the Adirondack to Montreal way back in '06 that stretch of track north of the border was largely 50 mph. I understand that it was down to 30 before the suspension. 60 would be nice, anything above would probably be pointless, especially since any time gained is easily lost with the typical customs delays. Would I consider taking Amtrak to Montreal today? Not a chance - what is the advantage? If they can demonstrate some level of commitment to providing reliable continuous service, perhaps a business class seat would be worth it. It's a long trip for coach!
I have a couple of clips from the Adirondack in
this video from when my brother and I took the train and met some friends who had driven up there. In '07 we went again and drove that time - I think that made it more like a 6 hour trip vs a 12 hour train ride!