Before you accept hearsay or rumors as "fact" when it comes to who may or may not be covered by the Railroad Retirement Act, you may want to check with the Railroad Retirement Board itself - or look up the Railroad Retirement Act of 1935. Frankly, if you're told that a particular Class 2 or Class 3 railroad does not provide RRA coverage for its employees, that company is violating Federal statutes (unlikely, since the penalties are severe) - or (more likely), the person who gave you the information is misinformed.
Let me quote from the Act -- 45 U.S.C. 231(a), parts i and ii:
The term "employer" shall include :
i. any express company, sleeping car company and carrier by railroad subject to the Interstate Commerce Act.
ii. any company which is directly or indirectly owned by, or under common control with one or more employers as defined in paragraph i of this subdivision, and which operates any equipment or facility or performs any service (except trucking service...) in connection with transportation of passengers or property by railroad.
Those provisions give the Railroad Retirement Board very broad jurisdiction. As I said in my earlier post, the Railroad Retirement Act mandates that employees of ALL common carrier railroads participate in the Railroad Retirement System rather than the Social Security System. By the way, when the term "common carrier" is used, I mean any railroad company handling freight in interstate commerce that is subject to the jurisdiction of the Surface Transportation Board (STB). (The language from the 1935 RRA Act refers to the Interstate Commerce Commission and the STB is the successor regulatory body for the industry.)
Switching operations (contract or otherwise) located inside an industrial facility are not common carriers, since they are not subject to the STB. Most museum or Disneyland-type operations aren't under the STB either, nor are light rail systems like the SF Muni, transit and subway lines like BART or the DC Metro, or a handful of intrastate-only industrial lines (Connecticut's Brantford Steam RR, the narrow gauge line operated by US Gypsum at Plaster City, CA and the Erie Mining RR come to mind.)
Other than the exceptions mentioned, you have a common carrier railroad --- and if it's such a railroad, employees are covered by Railroad Retirement.