The p51 shouldn't be enabled for that event so it must not have been set up right. In the future if you see a player in an unauthorized vehicle tell the CM who he is and the CM can take care of the situation, in the worst case he can eject the player if the player doesn't comply with the rules of the event.
The CM's have the ability to set the MOTD now so the rules should be clearly stated upon entering the arena. We're still at the begining stages, but HTC is giving us some realy powerful tools to use in running events. Set up and wait times should be greatly reduced realy soon
As for now the best way to get a smooth event is for the players to read the MOTD when they log into the arena. This should tell them where to go for what side. Then they should go to the mission planner and see if the missions are up yet. (Some CM's haven't started using the mission planner for events yet so this may not always be the case) With the mission planner we CM's can get the sides ballanced with much greater ease, provided the players play along with us

this helps to stop people from getting in the wrong plane too

Good things are coming

Udie