There is a briefing that occurs in the preplanning. First of all, there's the preplanning phase, where all of the partner agencies are involved in setting the parameters.
Then there are consecutive briefings right up to the actual event or the day of the event. There will be supervisors who are briefed, and subsequent to that there will be specific briefings with each team. Also, there will be general briefings with everyone there on the day of the event.
So there's a succession of briefings based on the same instructions that are provided to members. As well, depending upon the length of the event, there may also be booklets prepared for that event.