In addition to the mundane examples listed, there are also the Stringray Navajos operated by 2Excel to supplement the Northolt Flight Islanders in intercepting mobile phone communications. Allegedly, of course.
Basically advertise themselves as a cell tower and route calls, siphoning off the interesting ones. Pretty common technique in the USA as well.
Plenty of info on the public web if you have a search, nothing new revealed here. Not sure why people try to hush it.