No, it is not, according to the data sheet, 10.x and above, the CME docs does not list it, so it's likely it's only supported with fast track support right now.
● Cisco Unified Communications Manager Express: 10.x, 11.x, and later
http://www.cisco.com/c/en/us/products/collateral/collaboration-endpoints/wireless-ip-phone-8821/datasheet-c78-737346.html
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucme/requirements/guide/33matrix.html
HTH
java
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