http://www.knowth.com/loughcrew.htm

One of the many significant sites in Ireland aligned to the equinoxes. Archaeology tells us Loughcrew was used in the Iron Age so it falls under the header of 'celtic' site so its suitable for CR and under its popular name Slieve na Caillaigh (the mountain of the cultic cailleach to you guys) is a local centre of secular equinox celebrations today so its suitable for lovers of Traditional Irish belief too.

IMO it is a part of Irish tradition and could be a part of celtic tradition, though CR would probably want to stay away from the celebration given its strong links to the popular fertility cults.