Subject to this Act and to such modifications as are prescribed, the Assessment Act applies, in respect of any matter or thing in respect of the employment of a Commonwealth employee, as if:
(a) the employee were employed by the responsible Department and not by the Commonwealth;
(b) the responsible Department were a company and each other Department, and each authority of the Commonwealth, were a company related to the responsible Department; and
(c) the responsible Department were a government body.