Imho they are running the standard 'enemy IP' blocklists used by p2p filesharers for may years. Where one sees law enforcement using computers, one must first assume incompetence. In all likelihood he/she was using a machine at a known cop shop (Windows) without any sort of IP masking.
Some cops are highly trained IT specialists, but many investigators are actually just senior traffic enforcers who have been promoted into "technology crime" units. They have training and paper certifications, but lack any deep knowledge re technology. They make lots of mistakes. Think flowers by irene.