Realistically, finding someone based on a vhost is like aiming at a target 2km's away with a rifle that has a range of 1km.
Vhosts/BNC's and VPN's are used to stop people from doing what your doing - finding out who they are.
Best of luck
On paper its that way. but the most logical way is to just fake a government agency letter in 1 form or another and then get the company they used to hide the ip to give them the ip and can even get billing address's, names etc.
and its fairly easy to figure out who the person got the cloak from by using the ip that they had because it will trace right to the hosting company then to the company that runs the service.
BUT i think it would be fairly difficult to fake some thing this because a logical company would call the agency or court system to make sure its a legit request.