The_Dunner would prefer you not use it:
http://forums.dumpshock.com/index.php?s=&a...st&p=711620(At the time of the above post The_Dunner ran the Missions campaign so its an authoritative answer. Nothing to my knowledge has been posted about it since he responded in the above post.)
It has not been explicitly banned except that it requires GM approval which from the Catalyst Demo Team in my experience means an automatic 'no'.