I think it should be up to all three levels of government. It depends on the particulars of the disaster.
If it's a disaster in Trois‑Rivières that's relatively manageable, I think the municipality should be able to take care of it. If it's a major disaster, like the Lac‑Mégantic tragedy, I think the province should take responsibility. However, there are disasters that call for the involvement of all three levels of government. That's probably not what you want to hear, but I would say all three levels should take on that responsibility depending on the circumstances.