Fringe benefits tax was introduced to discourage employers and employees from coming to an arrangement whereby an employee would be paid in non-cash (salary) benefits, which would otherwise escape income tax for the employee.
In order to properly discourage it, the value of the benefit you receive is grossed up to the highest marginal tax rate. You have whats called a "reportable fringe benefits" label on your PAYG Summary which you then include on your tax return.
Ordinarily you can't salary sacrifice rent or bills. Health Service and Charity workers can still to a very limited extent salary sacrifice meal entertainment, but even that is becoming more difficult.
Note I am an accountant but not a tax practitioner (and I am also semi-drunk right now)... perhaps a proper tax expert can provide some better advice...