Every time I've seen them, they've had a chain around them, locked to a tree. Not sure how that's a 'public service'.
Here's the word from the guy that handles that. He drags the litter up to Lunch Rock each year. He's never locked it. The litter and wheel that was wrapped and locked is no longer there. It was locked over concern of liability and theft. It's gone. So it's just the litter at Lunch Rock.
IIRC, there was another litter maintained by the Friction Descent, which is gone. Apparently there are a bunch of litters stowed at the fire department in Idyllwild, they just need volunteers to drag them up to the rock.