How did it wind up in Indiana? Were they mailed from there?
It is a Twitter embedded video so you may get a twitter message and have to click to view it.
The trailers are at RR Donnelly in Seymour Indiana. The material inside looks like scrap paper from printing of mailers, or maybe the result of some of the mailers being damaged. They aren't ballots, and the trucks are not delivering mail. The trucks are probably used to move the printed direct mail pieces from RR Donnelly to the post office.
RR Donnelly is probably the company printing out the Trump campaign mailers. That is the kind of thing they do.