Most usually the BU doesn't test products/versions that are EOS when they FCS CUCM, the compatibility matrix shows they only tested 2.7
http://www.cisco.com/c/dam/en/us/td/docs/voice_ip_comm/uc_system/unified/communications/system/Compatibility/CSR-Compatibility-Matrix-InteractiveHTML.html
It *might* work, but there will be no official support for this integration.
HTH
java
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