Without prejudice to the application of Part III of the Act of 1991 to so much of any works authorised by the Tamar Bridge Acts as are major bridge works within the meaning of that Act, the said Part III shall have effect—
(a)in relation to so much of any works authorised by the Tamar Bridge Acts as are not major bridge works within the definition of the Act of 1991, but would, if executed by the highway authority, be major highway works within the definition of that Act, as if the Authorities were the highway authority; and
(b)in relation to so much of any works authorised by the Tamar Bridge Acts as are not major bridge works within the definition of the Act of 1991, but are of a description which if executed under powers conferred by Part V of the [1980 c. 66.] Highways Act 1980 would be works for road purposes within the definition of the Act of 1991, as if they were executed under powers conferred by the said Part V.