No provision of this act shall relieve, impair, or affect any right, duty, liability, or obligation arising out of any contract, concession, lease, or franchise now in existence except to the extent that such contract, concession, lease, or franchise may permit. Notwithstanding the foregoing provisions of this section, the Authority may renegotiate, renew, extend the term of, or otherwise modify at any time any contract, concession, lease, or franchise now in existence in such manner and on such terms and conditions as it may deem appropriate, provided that the operator of or under any said contract, concession, lease, or franchise consents to said renegotiation, renewal, extension, or modification.