After the filing of the proposed agreement with the executive officer, proceedings thereon shall be taken by the local agency formation commission in the manner and subject to the provisions of Part 4 (commencing at Section 56250, Government Code) of the District Reorganization Act of 1965. If the proposed annexation and agreement are approved by the commission, with or without amendment, wholly, partially or conditionally, it shall be mandatory for the board and the legislative body of the public agency to complete the proceedings for such annexation, subject to compliance with the commission’s resolution making determinations.