Hi Arco,
The GoogleMap implementation here (see the version 6.3 control converted to 6.4 download) is communicating both ways, although it doesn't report many events back to the Visual WebGui application, it does so for the ones it registers on the GoogleMap client side. See for instance the GoogleMap_ZoomChanged() JavaScript method which is invoked by the map control it self and registered within GoogleMap_Initialize. When raised, it will raise a Visual WebGui event which you can process within the FireEvent override of the server-side control and do whatever you need.
As far as I could see in my quick browsing of the BING map JavaScript API, you can indeed register event handlers client-side on the map and as long as the BING map supports raising client-side events for the operations you want to detect, you should be able to get that information to the server-side.
The challenge of wrapping the BING map control, as I see it, is not that you can't make this work, much rather that the API is HUGE and wrapping it all will require a lot of work.
Hope this explains,
Palli