Joint boards and port sanitary authorities under this Act, and the local board of health of any main sewerage district and any joint sewerage board constituted under any of the Sanitary Acts and existing at the time of the passing of this Act shall, for the purposes of their constitution, have like powers of borrowing on the credit of any fund or rate applicable by them to purposes of this Act or on the credit of sewage land and plant as are by this Act conferred on local authorities, and in the exercise of those powers shall be subject to the like restrictions ; and the Public Works Loan Commissioners may make any loan to any of the above-mentioned authorities which they may make to a local authority under this Act.