(a) Each of the following persons is an employer within the meaning of the act:

(1) Any carrier, that is, any express carrier, sleeping car carrier, or rail carrier providing transportation subject to subchapter I of chapter 105 of title 49;

(2) Any company—

(i) Which is directly or indirectly owned or controlled by one or more employers as defined in paragraph (a)(1) of this section, or under common control therewith, and

(ii) Which operates any equipment or facility or performs any service (except trucking service, casual service, and the casual operation of equipment or facilities) in connection with—

(a) The transportation of passengers or property by railroad, or

(b) The receipt, delivery, elevation, transfer in transit, refrigeration or icing, storage, or handling of property transported by railroad;

(3) Any receiver, trustee, or other individual or body, judicial or otherwise, when in the possession of the property or operating all or any part of the business of any employer as defined in paragraph (a)(1) or (2) of this section;

(4) Any railroad association, traffic association, tariff bureau, demurrage bureau, weighing and inspection bureau, collection agency, and any other association, bureau, agency, or organization controlled and maintained wholly or principally by two or more employers as defined in paragraph (a)(1), (2) or (3) of this section and engaged in the performance of services in connection with or incidental to railroad transportation;

(5) Any railway labor organization, national in scope, which has been or may be organized in accordance with the provisions of the Railway Labor Act; and

(6) Any subordinate unit of a national railway-labor-organization employer, that is, any State or National legislative committee, general committee, insurance department, or local lodge or division, of an employer as defined in paragraph (a)(5) of this section, established pursuant to the constitution and bylaws of such employer.

(b) As used in paragraph (a)(2) of this section, the term “controlled” includes direct or indirect control, whether legally enforceable and however exercisable or exercised. The control may be by means of stock ownership, or by agreements, licenses, or any other devices which insure that the operation of the company is in the interest of one or more carriers. It is the reality of the control, however, which is decisive, not its form nor the mode of its exercise.

(c) As used in paragraph (a)(2) of this section, the term casual applies when the service rendered or the operation of equipment or facilities by a controlled company or person in connection with the transportation of passengers or property by railroad is so irregular or infrequent as to afford no substantial basis for an inference that such service or operation will be repeated, or whenever such service or operation is insubstantial.

(d) The term “employer” does not include any street, interurban, or suburban electric railway, unless such railway is operating as a part of a general steam-railroad system of transportation, but shall not exclude any part of the general steam-railroad system of transportation which is operated by any other motive power.

(e) The term “employer” does not include any company by reason of its being engaged in the mining of coal, the supplying of coal to an employer where delivery is not beyond the mine tipple and the operation of equipment or facilities for such mining or supplying of coal, or in any of such activities.

(f) Any company that is described in paragraph (a)(2) of this section is an employer under section 3231. In certain cases, based on all the facts and circumstances, it may be appropriate to segregate those businesses engaged in rail services and therefore subject to the Railroad Retirement Tax Act from those businesses engaged exclusively in nonrail services and therefore not subject to the Railroad Retirement Tax Act. The factors considered are set forth in guidance published by the Internal Revenue Service.