I'm afraid I am going to have to disagree with a couple of things there, though it's off the original topic. I withdrew my post above as I realised I don't know as much as I thought about the non-WCDMA networks in the US, but I do know quite a lot about WCDMA devices.

3G does not "sit on top of" the GSM network. In the case of European networks plus AT&T and T-Mobile in the US it's a completely different technology called WCDMA. It may use the same basestations for cost and convenience but it'll be different electronics for the two types of network. This is why I originally questioned the use of GSM in ScottC's post. GSM and 3G are mutually exclusive.

I can't comment about how CDMA2000, EV-DO and CDMA co-exist on Virgin Mobile or other networks that use them, but WCDMA 3G networks operated by AT&T and T-Mobile operate the same way as the networks in Europe. They're different to GSM technology and not "on top of them".

You can buy products in Asia that are WCDMA-only, no GSM capability, and they will work fine in Europe though perhaps with reduced coverage.

Incidentally to make a final point, T-Mobile uses a different frequency set for WCDMA to just about everyone else in the world. Products designed for T-Mobile will probably have at least one more band in addition to the 1700MHz that nobody else uses, in which case it might work when roaming in Europe, but without knowing about other bands it's incorrect to categorically state "the device is capable of working in Europe" without more info.

That's all beside the point though. As you correctly state, a US-sourced Virgin Mobile device will not work in Europe.