20 C.F.R. § 202.7
The service rendered or the operation of equipment or facilities by persons or companies owned or controlled by or under common control with a carrier is in connection with the transportation of passengers or property by railroad, or the receipt, delivery, elevation, transfer in transit, refrigeration or icing, storage, or handling of property transported by railroad, if such service or operation is reasonably directly related, functionally or economically, to the performance of obligations which a company or person or companies or persons have undertaken as a common carrier by railroad, or to the receipt, delivery, elevation, transfer in transit, refrigeration or icing, storage, or handling of property transported by railroad.
20 C.F.R. § 202.7