So what I get from the docs on the NICS trans policy is:
The policy is drafted by officials in the Department of Finance.
There's a bit of consultation, and obviously NIPSA as the lead union has to be consulted. MM would seem to be the point man for collating responses to the consultation.
Based on the screening doc, the question is briefly considered of whether the trans policy would affect other protected groups, but that's answered in the negative so it's considered there's no need for a full equality impact assessment. (An EIA should theoretically flag up areas where you haven't considered the impact on a protected group, e.g. your disability policy works for wheelchair users but not for the visually impaired. In practice, institutions like the Welsh Government often take the approach of "we asked Stonewall and they said it was fine")
What I'm interested in is where the impetus for the policy came from. Not from NIPSA, who just did a response though were obviously happy to go along with it. (I suspect most responses in NIPSA were from the LGBT caucus, and most members didn't notice it.) And not from the DoF officials who drafted the policy, because the civil service works on inertia and someone would have had to have the idea and push for it to be adopted. I don't know who that was and it's impossible to tell from the paper trail we have.
But once the ball gets rolling, it's pushing at an open door (excuse the mixed metaphor), officials get drafting, they ask for advice from Stonewall or The Rainbow Project who are supposed to be the experts in this exciting new area, when they consult the union (whose members are very apathetic on non-pay issues) they get a positive response, and bingo, here's the policy and there are no SSS any more.
And all this very conveniently happens when the Executive is collapsed and there are no pesky DUP ministers around to object. It's a masterclass in institutional capture. There can't have been more than a handful of people actively pushing for the policy, but once it starts it can't be stopped.
And now of course, once the policy is bedded in, any challenge to it looks like taking rights away from trans staff who haven't done anything wrong.