The provisions of this part shall apply to copies of all contracts or agreements entered into by the U.S. Postal Service with any common carrier by rail or motor vehicle (including passenger-carrying vehicle), or freight forwarder, express company, or other person, for the surface transportation of mail as authorized by Chapters 50 and 52 of Title 39, United States Code, as revised and reenacted by the Postal Reorganization Act, 84 Stat. 719, 39 U.S.C. 5001 and 5201.