5 C.F.R. § 890.905
Limits on inpatient hospital and physician charges
(a) Hospitals may not collect from FEHB plans and retired enrolled individuals for inpatient hospital services more than the amount determined to be equivalent to the Medicare part A payment under the DRG-based PPS.
(b) Medicare participating providers may not collect from FEHB plans and retired enrolled individuals for physician services more than the amount determined to be equivalent to the Medicare part B payment under the Medicare Participating Physician Fee Schedule.
(c) Medicare nonparticipating providers may not collect from FEHB plans and retired enrolled individuals for physician services more than the amount determined to be equivalent to the Medicare limiting charge amount.