What you need to do is turn the Mobile Country Code (MCC) and Mobile Network Code (MNC) from the tower into a longitude and latitude which can then be looked up on a map service.
So you need to be looking for a database that stores this data like
cell2gps[
^]
or
opencellid/[
^]
Grab the codes from the phone, look up long and lat, map those to find location
/Darren
Edit: take a look at
Android Phone Status Sample[
^]
/Darren