Aye. I wasn't thinking they would learn anything in advance. They'd be assigned tasks on the fly, like "Defend this sector", or "Chase down and destroy that convoy and bring the ore to Pelatus. We'll specify the sector when you arrive".

Any bits that really need to be a surprise with no chance of leaks should be done without telling them. E.g. if there's a very critical ambush that must be a surprise, have the pirates working on some other task, and then once the ambush has been sprung, call them in as reinforcements. That would also help to give the "good guys" false information - even if the pirates were trusted, by having them appear to be busy elsewhere makes people think they'll be safe.

@Tarenty:
Information can be very sparse OR detailled in recruitment. Everything depends on event plot.
Back to "UBB Event", only two 'teams', the missions could be, simplified:

Nations) Goto (sector-1) and wait further instructions ; Wait Xmin ; Goto (sector-3) and attack the hive, kill all bots; Wait 2min ; Message(Surprise, some pilots are helping the hive. Kill'em'all!)

Gray) Goto (sector-2) and wait next orders; Wait Xmin ; Goto (sector-3) and support the hive, killing all its enemies. The bots will not shoot at you!

So, until Xmin after event start both teams have no clue on what they will do next.

the missions could be

Or they could not be.

As Proof of Concept, I made today a set of missions like I proposed. Who is in PCC can check there: 1598, 1599, 1604, 1605.

The host mission can spawn cappies, miners, escorts, privateers and hive.
Tunguska offers Mining and Escort missions in every station, while their rival, Orion hires privateers to disrupt event in Corvus stations. Mission lasts 30min or until the connie dies.

-4 missions, 3 roles, 2 opposing forces. Less than 1 day.