Basically, you need both your CC and your rental company to agree that the CC can cover your CDW.

I am leaving Friday, have a Plat MC with AT&T Universal Card, and am renting with AutoEurope. I'm told by MasterRental (the CC rental coverage) that I am covered, but that AutoEurope has the option to deny coverage. If there is any problem, she gave me a phone number for them to call to verify coverage.

I would call your CC, make sure it's covered in Ireland, ask for something in writing or a 24-hour number that can be called from Ireland (most 1-800 numbers don't work in Europe). Then call your rental company and ask if they accept CDW waiver.