I could be wrong, but I believe the city pays for the toilets. I say this because I've seen big homeless camps in random places all over the city, and a lot of them have toilets dropped off nearby that get serviced/cleaned out once or twice a week. I've even seen the standard residential style garbage and recycling cans dropped off next to camps that aren't anywhere close to homes/businesses. I can't imagine they're paying for their own toilet and garbage/recycling services.