Gave this another read alongside the script on which it is based. It's a lot more accurate than I realised/remembered. Virtually all of the dialogue is taken verbatim from the screenplay. In fact, other than a generally accelerated final act, the only real difference is with Halliday's death, which occurs significantly earlier and under different circumstances than in the script.
I still hate that the Space Commies fly USCM dropships, but I get the feeling that probably came from Fox rather than Christmas.