Clifford, please note that the information which is there in the Compatibility Matrix is always up to date and go through several reviews/checks before making it public. Now since 6945 is not showing compatible in SIP mode then I am pretty sure there would have been some technical roadblock which BU team might have encountered and hence it was not able to make to the list.
If you want an official answer to this, then I will recommend opening a case with Cisco PDI team and get it confirmed that way. Please ensure that you review the Overview document to ensure your company holds the required entitlement.
http://www.cisco.com/c/en/us/partners/tools/planning-design-implementation-technical-advisor.html
Regards
Deepak