LEED NC Addition Project Boundary Guidelines

After reading the MPR, and the MPR Supplemental Guidance from June 2011, I still have the same question that Tony mentioned above: "2. What if the building is an addition (structurally and functionally) but maintains separate HVAC systems? " Can a LEED NC project boundary for an addition include the existing building to which the addition will be attached? Must there be some criteria that are met in order to do so (such as major renovation to the existing building)? Or is the only option to have LEED NC for new construction only, and draw the boundary where the NC is connected to the existing building? Details: The existing building is not LEED EB. The NC will add over 100% square footage to the whole building. Thanks.