Your only train choice in Canada across multiple provinces, is VIA Rail.

http://www.viarail.ca/tickets/en_hora_intr.html

It is approx. 400+ kms. between Toronto and Montreal. We have used Via Rail for bikes, but only certain trains at departure certain times, can take bike (boxed).
The train station in Montreal is downtown...and is directly connected to the Montreal subway system. If you haven't been to Quebec, at least try Montreal for 1 day ...since the train station is just a few kms. from old Montreal...with 1600's era buildings and cobblestone. Actually as soon as you step outside of the train station, there are statues of 17th century Quebecois explorers and defenders.

Grog can speak better about Montreal since she lived there. I've been to Montreal several times.

Then you may switch trains to continue to Truro. We rode train during the night.

Canadian Maritime provinces can get cold weather starting even by mid-Oct. or so. Past few years they have been blasted with some whopper blizzards and lots of winter snow. When we were in Nova Scotia, we were told their growing season doesn't really start until end of May or later.