The Revenue tend to behave like God when it comes to questions like this. There is no clear definition as to what is or is not commercial. There is a tax consultant in Longford that is challenging the revenue on a number of these borderline issues. He has successfully argued that some jeep type vehicles with seats and windows are commercial and he has reclaimed vat thereon. He makes the arguments that these vehicles are not primarily designed for road use but rather for off road use - stronger chassis, bigger wheels, 4 wheel drives, etc..
As stated before the revenue's taxpayer charter is a joke. They do not act fairly towards the tax payer and the quality (and especially consistency) of advice given is often deplorable and like with much of Irish life no body is accountable - nobody gets the sack!.