A question about Carl...

Okay, here is another plot hole big enough to drive that semi through. When Murphy stops to have his shocks checked, a guy named Carl cuts his brake lines instead. Okay, so this guy is in league with Dr. Hale and company and is out to sabotage the big rig. That's all fine and well, but how did they get Carl into place so fast? They didn't have cell phones back then. And if they had him there in the first place, how did they know that Murphy would stop at that particular gas station long enough for the guy to cut his brake lines, or that he'd leave Carl alone long enough for him to complete his sabotage? Just another mystery of a bad t.v. show, like that stock car explosion question.