It's charitable. Cold snaps in Prairies can pretty easily hit -35, dropping down to -55 with windchill. You'll get frostbite on exposed skin in 2 minutes at those temperatures.
Most homeless will either take stay in one of the shelters available in the cities, or sneak onto the many freight trains heading towards the cities with milder climates when it starts getting cold. They'll head back when it starts to warm up again. A bus ticket is just enables the journey to be a lot more comfortable.