Section 13J. A health maintenance organization organized under chapter 176G may; (i) negotiate directly with any hospital with respect to such health maintenance organization’s rate of payment for hospital services; and (ii) enter into an agreement with such hospital reflecting such rate of payment without the approval of the executive office. The specification in this section of contracting rights of health maintenance organizations shall not be construed as affirming or denying such rights with respect to any other third party payer.