crime prevention billboards: aesthetic discipline?

The billboard at the Como-Snelling intersection has changed now. The "life or meth" billboard has finished its run, it seems (see my first post on the blog about that poster). Now we have a billboard warning people to lock their cars as theft prevention. It's interesting: Before I started the blog the other week I hadn't noticed this emphasis on crime prevention. I wonder whether the space is rented by the police or a crime prevention organization? If so, this raises the subject of how billboards are placed/used strategically as a form of aesthetic discipline. Then again, perhaps it's coincidence and the billboard is available to companies too (I'm sure I remember seeing billboards advertising products up there at some point). If anyone has insights, I'd be interested to hear them. And, aren't most of these owned by Viacom?