Local Government Act Article 24

Administrative organizations for enterprises jointly operated by multiple special municipalities, counties/cities, or townships/cities shall be established through approval by the relevant councils.When the aforementioned joint enterprise involves matters under the jurisdiction of the relevant councils, said matters shall be decided by a council engaged by the relevant councils.
中文原文 地方制度法第24條
直轄市、縣(市)、鄉(鎮、市)與其他直轄市、縣(市)、鄉(鎮、市)合辦之事業,經有關直轄市議會、縣(市)議會、鄉(鎮、市)民代表會通過後,得設組織經營之。
前項合辦事業涉及直轄市議會、縣(市)議會、鄉(鎮、市)民代表會職權事項者,得由有關直轄市議會、縣(市)議會、鄉(鎮、市)民代表會約定之議會或代表會決定之。

English translation for reference only; the Chinese text prevails. Not legal advice.