It’s my understanding the phone doesn’t care where the nearest tower is; assignment of the phone to a tower is done by the cell network management function.
All the phone cares about is whether it gets a response when it sends a connect-request.
couple years back GPS was incorporated.
Correct. The phone sends out a signal to register with the cell system...usually at a high power setting. The system responds and tells the phone what tower in which cell to connect to and at what power level...much lower than registration signal. The rest is up to the system while the phone is moving.