[Windows Mobile Apps and Games] cybermaus:
If done some serious searching, and as end result practically came no further than yourself. And in fact, with a working GPS in my phone, I am not sure I even know what I would need a cell based location for.

But still, out if curiosity, I searched, and I would like to mention:

Having looked into into location services a bit more, I find several mentions of corporate initiatives in the last decade that use server side locations. In fact, Motorola for example recently ditched Google's location service for Skyhook. On their Android phones no less.

I also found some academic papers. It seems some methods piggy back on timing of the time-division multiplex systems, some others use signal strength methods like we talked about. But all based on Cell and public WiFi towers and using multiple cells, made possible by the fact they are server side solutions.

Combine that with the fact that I know from personal experiance Google is placing me in the correct rural circle of a few acres in size, where there is absolutely no tower in or nearby the indicated circle, and not enough people to be a statistic area of interest, so I have to assume Google is using similar server side location services.

Which is a bit surprising because before I was assuming it would have to be handset side data, based on the fact they did a global roll-out in such a short time. Hard to believe they get all these providers synced up so quickly. Maybe E911 was further along than I thought. Either that, or the world really is governed by some Illuminati like secret world government....

But Illuminati or not, server side makes it out of our reach.

Like yourself Mach, I did find the RIL function to get the current tower and signal strength. I also found a Hayes modem AT command with the same info.

We would also need to have the original strength of the tower. This however could potentially be measured and put in a public domain database which also has coordinates. I believe such public databases are being collected in the open source domain.

But as you say, one tower is not enough, you'd need 3 at least and both RIL and AT function only provide one. I did find an obscure mention in a 15 year old reference GSM design mentioning the GSM radio is in principle tracking RSSI of 1 active and up to 7 non active cells, but no way to get that out of the radio by RIL or AT that I found.

On a more positive node:

Google Gears Geolocation API does allow one to simply request the location from Google and use it in one's own application. But I feel that would be cheating....

Edit: Or the more official W3C Geolocation API, which does not requite gears to be installed.

Edit2: I noticed the Geolocator on my Laptop was far more precise (a 10 mtr circle around my house) than my cell phone. Then I realized: though my laptop was cable connected at the time (docking station) WiFi was running, so it had a list of *private* WiFi stations (2 of mine and one of my neigbour). And I remembered I am on streetview and the streetview cars also collected private ESSID informaiton.

So I did a test and also started WiFi on my phone, even though I did not connect to it, just to the GPRS. And I started Google Maps again. And whammo, instead of the 500mtr radius circle I now had a 10 meter diameter circle around my house.

So that means that first of all Google indeed uses the WiFi ESSID info it collected from private access points, and second of all that the earlier 500 mtr radius was indeed done by GSM tower only.