Here are the answers for you:
Quote:
Are mobile safety cameras everywhere and do they often operate on tiny country lane
Technically speaking a mobile camera can operate anywhere that it could safely be parked up and have sufficient view if the road. However, mobile installations will be chosen by revenue return rather than safety grounds, therefore a small country lane with almost no traffic does not represent a financially viable site.
Quote:
are they usually set on busy spots where accidents happen?
As stated above, the sites are chosen purely on a financial basis, accident frequency has no significance. You are much more likely to see a mobile camera van on a dual carriageway that has a poorly posted 50mph speed limit and a large number of tourist motorists who don't know of this limit, than you are to see one on a road that has blackspot status, but low traffic through put.
Quote:
Also do they generally pull you over there and then?
No only police have the power to stop a moving vehicle.
[edit to remove the bit I misread]