The problem isn't whether or not he caught dodgy people. The problem is that in the process "I bet" he spied on a lot of people who were not dodgy, who had the right to have their privacy respected.
He worked on the technical support for targeted surveillance of serious organised crime and terror threats. So if you look at this realistically, no, his kit wouldn't have been used to spy on people who weren't at least suspected of being dodgy.