You also get to save the GST on the vehicle, but the novated lease companies often have inflated in-house finance deals. You can normally find companies that will do a bare novated lease (forget the correct term) where you can find your own finance and insurance, extras, etc... It really pays to do your homework here.
But if you get a quote, the FBT liability should simply be whatever they quote you for the after-tax contribution. That is essentially what you will save with the new proposed rules.