You can train in Ireland on a faa ticket for a JAA licence/rating . Its part of the conversion course and has been around along time now. Many ex PTC students like myslef converted and are flying safely these days. What you cant do legally is go solo but that shouldnt be neccessary. PTC being the wise business people they are are saving themselves alot of dosh in this method as the FAA certs are much cheaper.
One thing I can say in favour of the FAA ground school is that it maybe simpler and more straight forward but the is evey bit as good and much more practical. The JAA flight test however is much tougher in. IMO