The standing ogham stones were removed from the roof of the souterrain and placed in concrete by the excavators. Yes, there is another example like this in Cork with 7 or 8 ogham stones used in its construction - they were all removed to various museums after excavation. This site has 15 ogham stones. The souterrain found near Tara during construction of the M3 motorway had a stone with passage tomb art. Seems like the souterrain builders valued carved/incised stones, maybe they brought ‘luck’.