In this subchapter - (1) the terms "rail carrier" and "lessor" include a receiver or trustee of a rail carrier and lessor, respectively; (2) the term "lessor" means a person owning a railroad that is leased to and operated by a carrier providing transportation subject to the jurisdiction of the Board under this part; and (3) the term "association" means an organization maintained by or in the interest of a group of rail carriers providing transportation or service subject to the jurisdiction of the Board under this part that performs a service, or engages in activities, related to transportation under this part.