N.J. Stat. Ann. § 32:2-23.23

The purchase and ownership by the Port Authority of railroad cars and the rental thereof to commuter railroads of the States of New York or New Jersey are and will be in all respects for the benefit of the people of the said 2 States for the increase of their commerce and prosperity and for the improvement of their health, safety and living conditions and shall be deemed to be public purposes; and the Port Authority shall be regarded as performing an essential governmental function in undertaking such purchase, ownership and rental and in carrying out the provisions of law relating thereto.