District graywater recycling system

I am working on a large project that includes over 10 buildings. All 10 buildings are part of the same master site but only 8 of the buildings are part of our current scope and will be submitted for LEED 2009 under a campus approach with separate LEED submissions for each building. We are designing a district scale graywater recycling system that collects from and feeds all the buildings in the project including the 2 buildings not included in our scope in order to optimize the efficiency of the system. How do I reflect this approach in my calculations for the water credits? Do I include the graywater sources from the other 2 buildings but not the demands since they are not part of the LEED project? Or do I calculate the system as a whole even though 2 of the buildings are not included in the campus submission?