The following hospitals are exempt from any assessment under this chapter provided that if and to the extent any exemption is held invalid by a court of competent jurisdiction or by the centers for medicare and medicaid services, hospitals previously exempted shall be liable for assessments due after the date of final invalidation:
(1) Hospitals owned or operated by an agency of federal, state, or county government, including but not limited to western state hospital and eastern state hospital;
(2) Designated public hospitals;
(3) Hospitals owned or operated by health maintenance organizations under chapter 48.46 RCW; and
(4) Long-term acute care hospitals.