Some of them do - it varies.

I run forwards and rear cameras so that I can report dangerous/close passes. Strangely enough, I've had more issues with driver aggression (e.g. horn sounding) along the A370 than I've had with close passes. Of course, I've reported a fair few close passes in other areas (Avon & Somerset Police seem to be one of the few pro-active forces when it comes to dealing with video submissions).