Some of the more organized homeless encampments have porta-potties on site that are emptied on a regular basis. However, no one knows for certain where the removed waste is being deposited.
The problem that we’ve had in LA - and SF - is that the port-a-potties are taken over prostitutes to ply their trade - that and the homeless won’t use them.
I suspect it’s just too much effort to walk over to one when one is high on fentanyl - easier to relieve oneself right on the sidewalk.