Covenant of the state.

The state does hereby pledge to and agree with the holders from time to time of the bonds that the state will not limit or alter the rights hereby vested in the authority, the department, the county and the city to collect revenues and Hillsborough County gasoline tax funds and to fulfill the terms of any agreements made with the holders of bonds or to in any way impair the rights and remedies of such holders until such bonds and the interest due thereon have been paid. The state does further pledge to and agree with the United States and any federal agency that in the event any federal agency shall construct or contribute funds for the construction, reconstruction, extension or improvement of the system or any part thereof the state will not alter or limit the rights of the authority, the department, the county or the city in any manner which would be inconsistent with the continued maintenance or operation of the system or the construction, reconstruction, extension or improvement thereof and which would be inconsistent with the due performance of any agreements between the authority and any such federal agency. The authority, the department, the county and the city shall continue to have and may exercise all powers herein granted so long as the same shall be necessary or desirable for the carrying out of the purposes of this part.