Best guess... nothing changes.
What happens at the party?
- Asrabey asks for permission to go to the Bleak Gate
- Brakken finds out that the Jierres are in with the Ob
- The Jierres and Stanfield realize the RHC are onto the Bleak Gate facility
1. Doesn't lead to anything
2. Doesn't directly lead to anything
3. I don't think this leads to anything; there are a few points in the facility mission where it is clear the PCs retain the element of surprise, and Leone won't be lying in wait if the PCs have successfully stealthed their way into Borne's area.
I'd say you can probably skip the party, but you just as easily might as well accelerate the timetable so it happens just before the PCs head off. Give them a chance to meet Han and the other high-ranking Danorans.
The peace talks are (probably) cancelled as a result of Borne breaking out, not as a result of the PCs entering the facility.
One possibility is that without Brakken reading the Danorans' minds, the party won't realize that Han is in on the conspiracy as well, but I would expect most players to have guessed at that already.