At the moment CCTV can be put anywhere and be used for almost any purpose without the public being given and information or warnings. So a local authority can (or increasingly do) put up an unmarked camera to catch out people parking on a single yellow on a quiet street to pop into a shop to buy a pint of milk without them knowing they are being watched. Likewise people ar being caught out for "technically" breaking box junction rules though not actullay causing an obstruction because a car in front has changed lanes and they are left with their rear bumper just over the line again without knowing that junction is being remotely watched (this happenned to me). These CCTV cameras are often set up purely for income generation.
If I see a CCTV camera in a city centre, I would like to know who is watching. I might feel comforted if I know the polce are monitoring an area of crime, but at the same time I feel that my civil liberties are being breached if the type and purpose of surveilance is in effect being kept secret.