I see ads every now and then where someone is selling an "unlocked" 3GS, where it supposedly came unlocked from the factory.

Is this a scam? Or are there really such things?

I have heard that, for phones that came with ATT only from the factory, some older ones can be unlocked while retaining their original baseband. When this is done, the 3GS's GPS chip keeps running normally, and programs like Maps are pretty accurate.

But for other "ordinary" phones, if their software or baseband is too new, the only way to jailbreak/unlock them is to put the iPad baseband on them, 06.15.00. This let you use them with T-Mobile, but that baseband disables the GPS chip. So when you want to use Maps, it only gets fixes from nearby WiFi sources, which isn't as accurate as the actual GPS chip.

Does anyone know what the story is with these so-called "Factory unlocked" 3GS's? Do they really exist? If so, can you use them on T-Mobile, AND does their GPS chip run correctly?

Inquiring minds want to know!