One user claimed that Adobe tech support got him set for it to use PS CC, but we have no confirmation. It does not appear as easy as changing what program opens PS files.
The easiest solution is to keep PS CS6 installed, and just let it do the Encore menu editing. But I think I remember that the order of installs can affect whether that works or not.
Given all the issues, for users who had CS6, it seems to me that it makes sense to keep CS6 installed, then add CC.