Dozens of policing agencies are currently using cell-site simulators (CSS) by Jacobs Technology and its Engineering Integration Group (EIG), according to newly-available documents on how that company provides CSS capabilities to local law enforcement. A proposal document from Jacobs Technology,...
CSS are used to establish whose phone (the therefore who) is in a location and whose phone (and therefore whomst) sent and received data at what times.
That information is what police will use as probable cause to get warrants against the services you use if not your person or home.