Nobody has taken a case as it's unlikely to succeed.
The legislation is quite clear in what is allowed as a deduction for calculating rental profits:
S.97(2)(b) Any sums born...in respect of any rate levied by a local authority.
Is NPPR or LPT a rate? "Rate" isn't defined in the tax acts. You'd probably need to go back to Valuation (Ireland) Act 1852 to find a statutory definition (and good luck trying to find that!). But the generally accepted definition would be a charge levied by a local authority based on the value of a building.
So there's 2 things to satisfy:
1. Levied by a local authority
2. The charge is by reference to the value of the building.
NPPR satisfies neither. While it may be payable to a local authority it is not set by the local authority. It's also a flat charge without reference to the value of the building.
LPT clearly satisfies the second requirement. But (at present) it is not levied by the local authority.
The second relevant provision in the tax acts is S. 97(2)(c)
the cost of ... management of the premises...relating to and constituting an expense of the transaction...under which the rents...were received.
You could argue for a year and a day whether or not it is an expense of management of the premises. However, I think the important part of that section is the "relating to and constituting an expense of the transaction...under which rents were received". This implies a connection between the expense and the rental transactions. As NPPR and LPT are levied irrespective of whether the property is let or it would be difficult to argue such a connection. In addition Revenue could also argue that it's a tax and not an expense.
Minister Noonan has stated that it is planned to allow LPT as deduction in the future and will be done on a phased basis. Perhaps this will be done in parallel with the setting and collection of LPT by the local authorities.