Autodesk Labs released an FDO provider for Map3D and Civil that allows you to use Bing maps as a background!
It is very cool, but not supported on AutoCAD Utility Design yet, but if you want to use it on AUD install it on Map or Civil3D first and then you can grab the FDO files and copy them to the AUD install. From my testing it seems to work fine, but it is beta product and not supported at all in AUD.
What you need to do:
Bing Maps FDO:
Files to move (also attached) in \bin\FDO:
Project Basejump About Box.txt