The main requirement for a vertical km is that the top should be at least 1000m higher than the start. Looking at the map on the IMRA website, the start appears to be at about 150m altitude, so this race doesn't qualify, even though the descent and re-ascent between An Cahar and Carrauntoohill (both ways) take the total of climbing over 1000m.
I haven't got a map of the area, but from the IMRA map it appears that the valley bottom is at about 80m, in which case a vertical km in Ireland is probably not possible.