A board of park commissioners may by agreement with the legislative or other public authority in control of parks or park lands either within or without the park district, assume control of all or a portion of any existing parks or park lands or otherwise contract or cooperate with such public authority in connection with the use, development, improvement, and protection of parks or park lands. In such event, such parks or park lands may be developed, improved, and protected as in case of lands otherwise acquired by said board. This section does not authorize said board to acquire or control any park, park lands, parkways, playgrounds, other lands, or boulevards owned or controlled by any other public authority except by agreement as provided in this section.