http://www.nationaljournal.com/tech/...iders-20110929
this tells you about usa firms doing it.
but all mobile phone firms do.
the thing is they have to track you or they could not put the call to your mobile.
unlike gps it cannot say your say at a house, but i think its good enough to say your in a street.
but that was some years ago, so toy they may be more precise.
also the police tend not to want you to know this as they do not want criminals leaving phones at home. i amnot sure how much its used as evidence, but its at least gives police an idea if somone was in a certain area at a certain time. but that is if the phone is with them and switched on.