(b) With respect to an issue of consolidated transportation bonds sold after June 1, 1989, the Secretary may provide in the resolution authorizing the issuance of the bonds that there shall be deposited in the sinking fund maintained under § 3-215(c) of this title only the amounts of the proceeds of the taxes levied and imposed under § 3-215 of this title that may be required from time to time to pay the principal of and interest on the bonds, as and when due, and that holders of bonds of that issue shall have no right to receive payment from any other amounts deposited or maintained in the sinking fund. The Secretary may, at his discretion, determine that:

(c) With respect to an issue of county transportation bonds sold after June 1, 1989, the Secretary may provide in the resolution authorizing the issuance of the bonds that there shall be withheld and deposited in the sinking fund maintained under § 3-307(b) of this title from funds allocable to the county under Title 8, Subtitle 4 of this article only the amounts that may be required from time to time to pay debt service on the bonds, as and when due, and that holders of bonds of that issue shall have no right to receive payment from any other amounts deposited or maintained in the sinking fund. The Secretary may, at his discretion, determine that:

(d) The sinking fund requirements established for consolidated transportation bonds and county transportation bonds sold before June 1, 1989 shall remain unchanged so long as those bonds are outstanding and unpaid as if this section had not been enacted.