Thanks for the responses.
The amount of shaping a GM can do will depend on the mission. The story will be planned by one or two people, and so they will be outlining the mission that will be played in order to fit with the story line at that point. The GM team will then be the ones that use the GM console to play out the mission. This way, people coming up with the story can play in game (instead of always GMing) acting almost like an NPC by guiding the mission. The briefing for the GM might be quite broad, but at other points quite specific. One example might be: The division are going to explore sector ____ and will run in to light pirate patrols. They need to find a black box aboard one that they engage.
Sorry that is a bit vague. We’ll have to see how it goes.