If you look at the lower right hand corner below the map you will see the provider. They buy street maps directly from NavTeq, and are using Globe Explorer for their areal. I also see a credit for a company called Proxix and they are likely the ones who built the map/image server.

To your question though, you can completely customize the interface of VE to use your own navigation. A good example is

Search Property .

In the VE API we provide all the function calls for pan/zoom etc, and you just tie those into the mouse click events on the div you use to hold your navigation graphics. We also allow you to turn off our standard control so the map doesn't get cluttered.

Check out:

http://dev.live.com/virtualearth/sdk

it has all the details.
Mark - MSFT