Don't they have network effects? Let the locals search the next few towns over? Obviously this diminishes with distance; there's not a lot of benefit to Denver sharing with Minneapolis.

They do, but it's unclear how defensible they are. You don't have to operate Flock cameras to get access to Flock data (or Axon date) from neighboring municipalities; Flock even operates (last I checked) a subscription product for doing queries on their sharing network without their cameras installed.