I can't honestly say that if my local police force started podcasting that I'd hurry on over and subscribe.
Maybe I'm alone here, but does that sound likely? When I was a student, I didn't care less about the local police force - that was totally uncool and I can't imagine how much ribbing I would have taken had my cohorts found a police podcast on my massive Sony Walkman.
Sooner or later we're going to get a universal rating system for podcasts a la Technorati for blogs or Google for websites. Once we do, I'm going to be all over it to see what podcasts are actually being useful.