I don't have anything from USGBC, but I have some history from ASHRAE. There are a series of interpretation requests to ASHRAE 90.1 about how handle AC systems serving primarily process loads. It is clear that ASHRAE considers AC systems serving primarily process loads exempt from requirements of ASHRAE 90.1. Since they don't have to meet minimum efficiencies, they need to be modeled the same when demonstrating compliance with ASHRAE 90.1. See interpretation 4 about a theoretical central plant that is used mainly for IT cooling.

"The central plant is exempt from the requirements of Standard 90.1 and should be identical in both the Proposed Building Design and Budget Building Design."

The interpretation is worded for Chapter 11, which is another means to show compliance to the standard. However it is interesting to note they are no longer applying this interpretation to Appendix G of 90.1-2007. This seems like a logical progression sense Appendix G is meant to show energy efficiency not compliance.

"This interpretation also applies to Section 11 of 90.1-2007 as well as Appendix G of 90.1-2004 but does not apply to Appendix G of 90.1-2007."

Perhaps that knowledge may be helpful.

~Reba