we have learnt from experience that cell phones are like big trackers, the authorities can and will use your phone to pin point your position through either Gps or triangulation and this has happened, each cell tower you pass or are within proximity to leaves a record / log and I personally have seen these logs

there are apps that tell you, your nearest cell tower and they like computers these days

the government use what is called a IMSI-Catcher to spoof a cell tower signal and trick your device in to connecting to it, the more advanced ones seem to capture lots of personal data such as text messages and possibly even phone calls

There are good people out there working on IMSI Catcher detection apps such as this one on xda forums

There is a more detailed article about IMSI Cather detection I have no association with these websites, they are something I have found during my research.