In northern Ontario and Quebec, there are large forests between the urban areas. You can easily overnight in logging road turnoffs. In Ontario, when you get north or west of Timmins it really opens up. I just parked along side the road to overnight. Maybe one car an hour during the day, one or two during the night on the road from Chapleau to Timmins, for example. Timmins is the "big city" in northern ON. I haven't been there but ON north of Lake Superior must be quite wild. Thessalon to Chapleau is another very nice wilderness road.
Quebec is populated much further north than Ontario, with a lot of farms. You can go to fine dining restaurants even as far north as Rouyn-Noranda, a very nice little town on the edge of civilization. They also have great poutine. If you keep going further north, north of Matagami, you enter the James Bay Region. On the paved road between Matagami and Radisson, there is one gas station/convenience store on the main road (620 km). There are several Cree villages on the coast, but you have to ride about 100km of gravel road to get to the coast from the main road. The Cree speak English, most everybody else speaks French. Some French speakers don't speak much English. You should know how to say bonjour, souviplay and merci, you will be embarassed if you can't say the basic polite words.
Along the James Bay road, there are free campgrounds every 100 kms or so, usually near rivers and lakes. There are also many two tracks headed off into the forest.
I did this trip in 2009, it was the best adventure road trip that I have ever done. Remote wilderness, wide open spaces, almost no people, bears, empty highways, wild rivers and native villages.
There are not many people up there. You might pass a car an hour on the main road.
https://www.google.com/maps/dir/Sau...38eee2549c!2m2!1d-77.616743!2d53.792039?hl=en
http://wikitravel.org/en/Baie-James