(a) The department may lease to public agencies or private entities for any term not to exceed 99 years the use of areas above or below state highways, subject to any reservations, restrictions, and conditions that it deems necessary to ensure adequate protection to the safety and the adequacy of highway facilities and to abutting or adjacent land uses. Authorized emergency vehicles, as defined in Section 165 of the Vehicle Code, which are on active duty and are not merely being stored, shall be given preference in the use of these areas, and no payment of consideration shall be required for this use of the areas by these vehicles. Prior to entering into any lease, the department shall determine that the proposed use is not in conflict with the zoning regulations of the local government concerned. The leases shall be made in accordance with procedures to be prescribed by the commission, except that, in the case of leases with private entities, the leases shall only be made after competitive bidding unless the commission finds, by unanimous vote, that in certain cases competitive bidding would not be in the best interests of the state. The possibilities of entering into the leases, and the consequent benefits to be derived therefrom, may be considered by the department in designing and constructing the highways. Revenues from the leases shall be deposited in the State Highway Account. If leased property was provided to the department for state highway purposes through donation or at less than fair market value, the lease revenues shall be shared with the donor or seller if so provided by contract when the property was acquired. If the donor or seller was a local agency which no longer exists at the time the department enters into the lease, the local agency's share of lease revenues shall be paid to the county or counties within which the local agency was situated.