*Spoiler involved*

I beleive it was some of the "runners" who had been out drinking. It is the same green chevy that shows up at the end for the "tug of war" scene.

Some of the water tower conspiracy gang, I think. There are two men dressed in white (shirts at least) standing in the open sunroof. Presumably there's a driver and there's at least one person in the back seat (if you go through the scene screen-by-screen you can see a silhouette against the skipping girl's white house at one point).