Ky the "open neutral" scenario is not the reason for the rule about regrounding the neutral. They just don't want voltage gradients within the building. When you get to the next building, with a new ground electrode system, you can start a new "pseudo service" regrounding the neutral ... as long as you don't have a bonded metalic path back to the previous building.
The ramifications of an open neutral in building #2 are exactly the same as one in building number one.
