Okla. Stat. tit. 19 § 351.3
The board of county commissioners of each county may enter into agreements with any nonprofit volunteer or full-time fire department organized pursuant to Section 592 of Title 18 of the Oklahoma Statutes or any rural fire protection district created pursuant to the provisions of Sections 901.1 through 901.29 of this title for the furnishing of fire protection services by such entities for all persons and property located in the unincorporated areas of the county. The board of county commissioners of each county may pay for such fire protection services on such equitable basis as may be agreed upon and the costs of such fire protection services may be paid out of the county general fund or the county highway fund.
Okla. Stat. tit. 19, § 351.3