I know that when I worked there, BT often used to ask for such surveys to be performed when they couldn't track down the source of interference to ADSL broadband connections. In one particularly egregious example there was a source that knocked out the broadband connection for much of a village every evening at 6pm. It took quite some time to track it down because the interference source was short-lived. Turned out to be an burglar alarm arming.Yes, they are used to detecting Pirate radio and to trace sources of interference.
I guess this is less common now that fibre connections are becoming widespread.
I can't confirm if they were also used to detect televisions.