I show them on B3 in Bracebridge, A1 around Algonquin Park and C3 over towards Parry sound.
You can cross reference the channels with the actual frequencies here:
http://www.radioreference.com/apps/db/?aid=4179
Dispatch typically uses cell phones to call the trucks. It's only when a group of trucks are close together that you'll actually hear anything.
I was up in Muskoka last month after the wind storms and only heard truck to truck comm's. I think they were using 49.130MHz.
On Monday in Erin, the crews were using 48.950MHz.
I created a favourites list of all the Hydro One channels and scan that when I'm out working on storm clean up duty. If you've got room in your scanner, I'd dump in all the channels.