I understand that REVIT allows worksets attached to a master file. Any reason that two offices cannot keep synchronized master files and have local sharing?
As Revit stands now this isn't possible. If you could find a way to synchronize the central (master) files I could see this as being helpful. It might speed up the saving process. The central files would need to be continually updated though.
Check out Riverbeds Steelhead Appliances. They've got hardware that lets a WAN act like a LAN. I've used it and it works great. This is the only way that I've found to work effectively on a Revit model in multiple offices.