Other towers can still passively track your signal. You also have to communicate with more than one tower during handoff between cells. This is a capability mandated by E911.

From https://en.wikipedia.org/wiki/Enhanced_9-1-1:

  To locate a mobile telephone geographically, there are two general approaches. One is to use some form of radiolocation from the cellular network; the other is to use a Global Positioning System receiver built into the phone itself. Both approaches are described by the Radio resource location services protocol (LCS protocol).