Hi Gear,
Just as an FYI for future reference, this info is found in the IP Phone Data Sheets. It's hard to find anywhere else :)
Cisco Unified IP Phone 6900 Series
Signaling protocol support
The phones are supported in Cisco Unified Communications Manager and Cisco Unified Communications Manager Business Edition Versions 7.1.2 and later using Skinny Client Control Protocol (SCCP).
http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/phones/ps10326/data_sheet_c78-541199.html
Hope this helps!
Rob