You should be able to do this... there isn't a doc lying around on it, it's kind of an unusual thing to have to do.
Before you move you're keys, be sure to adjust your COS settings "licensed features" on your system currently with UM such that no one has TTS or VMO licenses enabled... then when you swap the keys it should be OK provided they have the proper number of users/ports licensed on them (i.e. if you put a key with fewer ports on a box, the "left over" ports will not function).
