DAB is for real, and uses same kit as in the UK. It's not a trial, but it's not available generally yet. Don't get excited though, it's mainly a mechanism for getting more stations onto less frequency space. While digital, there's quite a bit of compression involved and it doesn't always sound so good when heard on headphones or a HiFi. Mainly, there's the convenience of station names and track info.
DTT (Digital Terrestrial Television) is still being tested and don't buy anything until it's launched. Existing UK DTT equipment will not work with the new Irish DTT system when it goes live as the Irish system will use a newer technology.