(1) Any two or more port districts shall have the power, by mutual agreement, to exercise jointly all powers granted to each individual district, and in the exercise of such powers shall have the right and power to acquire jointly all lands, property, property rights, leases, or easements necessary for their purposes, either entirely within or partly within or partly without or entirely without such districts: PROVIDED, That any two or more districts so acting jointly, by mutual agreement, shall not acquire any real property or real property rights in any other port district without the consent of such district.
(2) A district may enter into any contract with the United States, or any state, county, or municipal corporation, or any department of those entities, for carrying out any of the powers that each of the contracting parties may by law exercise separately.
(3)(a) A port district that is located in a county that has a contiguous border with another state, and a population between fifty and seventy thousand, may enter into any contract that each of the contracting parties may by law exercise separately with, including but not limited to, municipal corporations of adjoining states.
(b) In addition to other powers granted by statute, a port district that is located in a county that has a contiguous border with another state, and a population between fifty and seventy thousand, may enter into agreements with the United States or any of its agencies, or with any state, or with any municipal corporation of this state or of an adjoining state, for exercising jointly or cooperatively within or outside the district, in whole or in part, any of the powers that each of the contracting parties may by law exercise separately, for the promotion or development of trade or industry. Such powers may be exercised outside the boundaries of this state only after a public hearing of which notice has been published in a newspaper of general circulation within the district at least ten days in advance, and pursuant to findings and a resolution by the port district's commission that: (i) The undertaking and the district's participation in it will substantially benefit the district and the state of Washington; and (ii) the districts' share of the cost will not exceed an amount calculated by dividing the total cost of the undertaking by the number of participants.