After the county commission has adopted the subdivision regulations, no plat or instrument describing a subdivision of land within the unincorporated area of the county shall be recorded or vacated until the plat is first submitted to the planning board. No plat shall be approved in any county in which emergency telephone services or central dispatching services are provided and funded pursuant to sections 190.300 to 190.329, unless any requirement by the governing body of the county or of the board established pursuant to section 190.329 to provide such governing body or such board with maps and site plans of the subdivision so that the subdivision addresses, streets, drives and roadways may be added to and included in any computer database used in conjunction with providing such services are met. The board, after hearing, may vacate any plat of a subdivision of land including roads, streets, highways and alleys. At such hearing, the board may require that expert witnesses providing evidence be sworn in so that their statements are statements made under oath. Upon the vacation of the plat, the recorder of deeds shall be notified in writing of the vacation. If the county planning board does not report upon the plat within thirty days, it may then be deemed approved. If the plat is amended or rejected by the planning board, such action may be overruled and the plat approved only by the county commission, after public hearing. The reasons for the overruling shall be spread upon the minutes of the county commission. The recorder of deeds shall not record a plat of a subdivision of land in the unincorporated area of the county until the recorder has received a certificate of authority from the county planning director, who shall issue the certificate if the plat has been approved, pursuant to the provisions of sections 64.211 to 64.295. The county planning board may, upon written request of the legislative body of an incorporated area in which there is no municipal planning commission, pass upon subdivision plats within the incorporated areas, and the plat shall be subject to all rules and regulations of the county planning board and shall not be recorded until it has been approved in the same manner as a subdivision plat in an unincorporated area. If the county planning board does agree to pass upon plats in an incorporated area, the county recorder shall be advised of the fact by registered letter from the planning board and the municipal legislative body.