From what I've heard, a group of car thieves will "lead" with one perp stealing a large truck to bash through the fence, gate, whatever. Then the remaining thieves drive out through the gap.I'm not clear on this. Don't factory storage yards have the ability to build fences and gates? Maybe hire a night watchman or two ?
The assembly plants I know of cover around a square mile. That's 4 miles or so of fencing. The thieves just search out the weak point. And yeah, I would bet that some plant worker(s) have some involvement.