There's still a ton that the police have yet to release, but this seems to be consistent with the AP report on the viewing of Twin Peak's CCTV tape.
Yes it was a pre planned event and they weren’t invited because they were not part of the organization sponsoring the meeting. That’s probably why they got there early.
“Cossacks where already at the restaurant, the Banditos pull up, and the Cossacks crashed the party? A ‘party’ that was a confederation of colors?”
The ‘party’ was a meeting called by the Bandidos and the place of the ‘party’ was reserved by the Bandidos. The Cossacks did not pay the proper extortion fees to the Bandidos.