49 C.F.R. § 243.205
(c) Railroad oversight. Each railroad shall identify supervisory employees, by category or subcategory, responsible for conducting periodic oversight tests and inspections for the safety-related railroad employees that it authorizes to perform safety-related duties on its property, except a railroad is not required to:
(e) Railroad oversight for contractors. A railroad may choose to require supervisory employees to perform oversight of safety-related railroad employees employed by a contractor either:
(g) Contractor oversight. Each contractor shall conduct periodic oversight tests and inspections of its safety-related railroad employees provided: