I'm trying to keep the organisations out of PC plots, they can work in the background. But if you bring in IRIS, I'll bring in SERT, and I daresay the two won't get along.
International organization fight! Joking aside, fairly certain it would be justified for Murder Night.
I will be fine with the either IF any involvement of additional organizations corresponds to Murder Night deploying more units at an equal or higher rate. By which I mean armed escalation to all out conflict (and use of IACs if any more WSC or compatible units get deployed).
Well, the place does look like a magic circle...