Hi Vlad,
In softphone mode, the Jabber SDK requires a device to be configured in CUCM. The device must be of type "Cisco Unified Client Services Framework" (CSF). The device name can be any name. By convention the SDK expects a device called ECP{user}, where {user} is the CUCM end user id. This can be overridden by the application, in the devicesAvailable callback of the registerPhone function (cwic API).
The CSF device type is supported from CUCM 6.1.3+, so the reply to your question is "no", CUCM 8.6.2 is ready "out of the box" to be used by the Jabber SDK.
Thomas