Depending on which trains were "thrown away," how many, etc., a container load could easily be worth $50,000-$100,000 or more. I think that's enough for felony theft. And an investigation may uncover other instances of wrongdoing.
If the goods were transported by (or the information was shared for nefarious purposes by) UPS employees and not the US Post Office, then I don't think the Postal Inspector would have jurisdiction.
My personal experience with an identity theft incident is that local police aren't willing or able to get involved with crimes that begin or end outside of their limited geographic jurisdiction. If the shipment allegedly went from Pennsylvania to California (i.e., across state lines), then as I understand the responsibilities of US law enforcement agencies, it would be the purview of the FBI.
I know that several years ago, based on a tip from a private citizen, the FBI investigated and prosecuted wrongdoing associated with the McDonalds Monopoly promotional game. So sometimes they DO get involved in what seems like "small stuff." If you are an aggrieved party in this case and pay taxes, then you have a right to request an audience with an investigator, and share the details of what you were told. And if any of the trains DO eventually surface, then I would DEFINITELY pursue a criminal investigation.
I guess part of me feels that if we just let this go, it'll happen again. My $.02.