Yes, as defined as replacement of a vehicle’s propulsion system, including replacing a propulsion system with a propulsion system of a different type (e.g., replacing a diesel engine with an electric battery propulsion system).  Rolling stock repowering is permitted for buses that have met at least 40 percent of their useful life; in which case, it must be designed to permit the bus to meet its useful life requirements.  Rolling stock repowering is permitted as part of a rebuild; in which case, it must extend the useful life by at least 4 years.