I does appear that Revit Server can provide WorkSharing on a Revit Project in a WAN environment.
http://wikihelp.autodesk.com/enu?adskContextId=EXLINK_RS_OVERVIEW&product=REVIT&release=2013&languag...
What about WAFS, Globalscape or Peersoft?
Globalscape recommends SUBST command to prevent Revit from resolving Drive letter to UNC path.
Comment, discussion, please...