Yeah, go for a walk down the Arakawa or Sumida embankments (not right now, I guess, given that was all recently underwater) and you'll find some semi-permanent camps in a good state of repair. Talked to some of the guys by one and apparently they've got a pretty strong culture of self-enforcing cleanliness and not messing with the civilians, since they'll get cleared out if the cops get legitimate complaints from people in the area