DES Option 1 - Baseline System Heating Type Clarification

We're using Option 1 of the "Treatment of District or Campus Thermal Energy in LEED v2 and LEED 2009 - Design and Construction" document to comply with EAp2 / EAc1. Our proposed building will utilize purchased steam and purchased chilled water from the existing central plant. Per the document, for Option 1, only downstream equipment is accounted for and the energy source is modeled as purchased energy in both the Proposed and Baseline cases. Given the size of the proposed building, system 7 will be the primary baseline system. Per ASHRAE 90.1 table G3.1.1B, this system is a VAV packaged rooftop unit with reheat and has chilled water as cooling type and hot-water fossil fuel boiler as heating type. According to table 3 (Option 1) of the DES guideline, no changes are required for system 7. Does this mean we can model an 80% efficient (per ASHRAE 90.1 efficiency requirements) boiler that uses purchased steam as its fuel source (in lieu of gas or other fossil fuel) as the heating type for baseline system 7? Would this approach still keep the DES cost-neutral, as required? Any feedback would be greatly appreciated. Thank you.