A majority of the political subdivisions within a sewer subdistrict formed pursuant to sections 204.565 to 204.573 and entitled to representation on that subdistrict’s advisory board under section 204.571, together with the board of trustees of the common sewer district of which the subdistrict is a part, may petition the circuit court in which such subdistrict was formed for extension of the boundaries of such subdistrict and common sewer district within one or more of the political subdivisions or to include all or a part of other political subdivisions, which political subdivisions must also join in such petition. The petition shall state the purposes for which the subdistrict is to be expanded and shall have a map of the subdistrict, including the proposed expansion, attached thereto. The court shall schedule a public hearing and notice shall be afforded in the same manner as provided in section 204.567. If the court shall find such expansion is reasonable or necessary, the court shall enter a decree extending the boundaries of the common sewer district and the sewer subdistrict, declaring such area to be a part of the sewer subdistrict and common sewer district, and approving the map submitted by the petitioners. The decree and map shall then be filed in the same manner as prescribed in section 204.567.