Any city or county aggrieved by any decision of the department, under the provisions of Division 3 (commencing with Section 2004.5) or under the provisions of Sections 186.3 and 186.5, may, within 30 days after such decision, petition the commission for a hearing. If a petition is filed, the commission shall hear the petition as soon as conveniently possible and after reasonable notice to such city or county. The commission shall make its order allowing or disallowing the petition, in whole or in part, and the commission’s order shall be final and conclusive.