The tower doesn't need to know your location for that to happen.
Actually in CDMA, they do, to get the timing-advance that allows soft-handoff to work. It's down to tens of nanoseconds to make the chips line up when they're received at your location, and that means the trilateration accuracy is down to tens of feet.
Also, all modern standards are based on CDMA for the air-interface portion, because it's so efficient.
Look up any of the hyphenated terms if you care to learn more.