Any licensed provider eligible to receive Medi-Cal reimbursement under law and who enters into a written contract with the authority under terms and conditions approved by the department shall be able to participate in this program as a provider. A written agreement shall not be required if any of the following circumstances apply:
(a) The provider renders any medically necessary emergency health care on a nonroutine basis.
(b) The provider renders services that are duly authorized by the authority, if the services are either seldom used or are rendered outside of the service area.