Medicare Ambulance Access, Fraud Prevention, and Reform Act of 2019 This bill establishes a series of requirements relating to coverage of ground ambulance services under Medicare. Specifically, the Centers for Medicare & Medicaid Services (CMS) must continue to designate an area as a rural or qualified rural area that is eligible for increased payment under Medicare, even if the area would otherwise no longer qualify for such designation, if the area has a specified population density. The CMS must also establish an administrative process to allow ambulance service providers to appeal a change in an area's designation. The bill also requires the CMS to (1) expand to all states a prior authorization model for repetitive scheduled nonemergent ambulance transport, in accordance with specified limitations, if such an expansion has not already occurred by a certain date; (2) increase payment rates for ground ambulance services; and (3) eliminate certain administrative requirements for such services.