The purpose of §§ 6-406 through 6-410 of this subtitle is: To avoid duplication of effort by the Administration and Baltimore City, to the extent that they have coextensive authority in matters relating to harbors, docks, wharves, and port development; and To assure the uninterrupted continuation of needed services. The duty to exercise all authority in this field continues in Baltimore City to the extent that the authority has not been transferred to the Administration by agreement made under § 6-407 of this subtitle. If, by agreement made under § 6-407 of this subtitle, Baltimore City transfers to the Administration any duty, only the Administration may perform that duty. Any ordinance or regulation that was adopted before June 1, 1959, by the Mayor and City Council of Baltimore and that relates to any authority transferred to the Administration by agreement made under § 6-407 of this subtitle: Continues to be in effect, except as otherwise provided in this subsection; Has the status of a regulation adopted by the Administration; and Like other regulations of the Administration, may be readopted, amended, or repealed by the Administration. Only the Administration may readopt, amend, or repeal these ordinances or regulations.