The fuel tax credit scheme is an almost A$6 billion subsidy each year to industry. ... The fuel tax credit scheme rebates excise tax to those businesses that consume diesel on non-public roads
That sounds quite fair and reasonable to me.
And it is NOT a subsidy.
It is a reduction in tax that would have been payable.
Perhaps it would be clearer if we were to use the term incentive rather than quibble about the difference between a tax reduction and a subsidy.
In my view, it is a rebate for a tax that should never have been levied. The fuel tax is 'meant' (ha ha ha !!!) to be for road maintenance, so if the fuel is being used for non-(public) road use, then the tax should never have been applied.