AIS (and probably other operators but I haven't worked with them) have a solution in place which records all network traffic coming through their mobile network. They are storing this data for different amounts of time after they run the data through various classifications and algorithms. Along with storing a history of sites being visited by using the HTTP flow they are also storing details such as location of subscriber per transaction, applications they have installed, favorite apps, most visited sites and many many others. So its possible for them to build a map to see where a user's location changes during the day. They are not actively reading everyone's messages unless there is an order from the police to track a particular user's history. The major function at the moment is just for providing reporting on where network congestion, predicting customer churn and other things.
The tools that they are using to do this are called CEM (customer experience management) and have existed for a few years now. Many vendors such as huawei CEM, ericsson do this for them.