It's just an irregularity. Although Eire doesn't take the article in the nominative, it USUALLY requires the article in the genitive. Usually you see the article omitted in official terms like, "Dail Eireann," "Bus Eireann," "Raidio Telefis Eireann," but "na hEireann" is more common.
Since "Ireland" is a definite noun, the noun it modifies as a genitive (in this case, "foireann") doesn't take the article.
I have submitted a problem report saying that "The Ireland team won" should also be allowed. I think it is quite common to use the country name when talking about the national team, of some countries at least, in particular, England, Scotland, Ireland & Northern Ireland. eg this quote from gettyimages.co.uk "The Ireland Team Wins The Alfred Dunhill Cup"