In the exercise of its powers within the boundaries of the public authority, a public authority is exempt from the motor carrier act, Act No. 254 of the Public Acts of 1933, being section 475.1 to 479.20 of the Michigan Compiled Laws; Act No. 3 of the Public Acts of 1939, being section 460.1 to 460.8 of the Michigan Compiled Laws; and Act No. 432 of the Public Acts of 1982, being section 474.101 to 474.141 of the Michigan Compiled Laws.