I don't know if it was involved here, but "spectrum monitoring" (that's the keyword for more information about equipment you can get and who the expected customers are) is definitely a thing that is done in many places, and not only by the military, but also by police and regulators. It's not clear where the mast was installed (the CoL police aren't specifically limited to that very small area and one arrest was South London and one was Manchester) but if it was in central London, as a glaring terrorist target with an airport (London City) and heliport, I'd be very, very surprised if there's nothing watching the spectrum. Whether the operators of the spendy gear would share the information up for such "petty" crime, I don't know.

And there's always the Ham community who really, really hate spectrum abusers.