you might check out www.riverbed.com
i think it's basically a fast WAN but i'm not a network guy so i could be totally off my rocker
i'm about in tackle my first revit job with multiple architectural offices (and it's also my first revit job period so that should be interesting) so i'm faced with the same issues you are. i'm thinking that the best strategy i've been able to come up, so far, is to break the building into separate linked files (maybe shell and interior?) for each office. not sure i like it but, in concept at least, it's no different than how i've worked in AutoCAD before so i know, believe, it will work.
another idea i had, though untested, is to have two copies of the central file (one in each office) and use worksets to attempt to isolate whose doing what and to also use Coordination Review or Interference Check to catch the inevitable changes to associated elements