vega is the orange dudes. I've always set the game speed a little lower for this one...
what you do is blitz to the scrin ship and use your buggys & bike to kill the wolverines.
put an eng by in the scrin ship. and head downward & leftward to the ramp & broken bridge.
As soon as you get up the ramp, the train is going to leave. when it gets to where you are, an engineer will try and repair the bridge. KILL IT!!
then take out the train and get the crate to finish the mission.
Sometimes when i feel like burning time I use my other 2 engineers to capture the orange conyard and refinery, and eventually take over the whole map