That is a rather arbitrary distinction to draw when deciding what service is provided to a community. How many indigenous communities on a provincially regulated railroad get the level of service that VIA provides to these communities on federally regulated railroads? If there is a difference, how exactly do you justify it to the community that gets worse or no service?
In Ontario, the only First Nations Community (i.e. 'Reserve') that I can think of that is served by a provincially-regulated railroad is Moose Factory (indirectly - it's on an island). I am aware that there are First Nations-operated roads in other provinces but I don't know how they are regulated. All other First Nation communities in Ontario are serviced by road connected to the provincial road network or an airport operated by the MTO. It was a decision made by the Ontario government years ago to build and operate airports in remote FN communities in lieu of building year-round roads.
I would assume that any sleeper car operating as part of a DMU consist would not be a DMU but simply a sleeper car linked in.
That said, I think DMUs would really only come in to play on the Senneterre, Jonquiere and White River trains, where only 2-3 pax (DMU) cars and a (unpowered) baggage car may be needed. And those could have commonality with DMUs used out of the Kingston hub after HFR, where using Chargers may prove to be overkill.
To me, a configuration that accommodates sleeping implies eating and likely baggage. In remote service, baggage service includes the need to accommodate canoes, ATVs, MSVs, large game, etc. I suppose that could all be woven into DMU layout. DMUs are, by their nature, self-propelled, but I'm assuming there are limits to how much unpowered weight they can haul.