It is possible to track a phone, there are various companies that do it. My boss has been looking into it so they can keep track of his dad who goes for long walks and gets lost, and is diabetic so they need to find him.The good news is that its not very accurate, the system uses the aerial masts to triangulate your position, The most accurate they can be is 150 meter radius but its normally about 2 - 3Km radius, so not that good really.
If you're worried then change your phone.
Mobilspionage