Fantastic! This is obviously a different day in April 1971; A3 was re-engined in March of that year, and A15 in May, so it must be April! Looking at the weekly circulars, that's the day when the two "A"s arrived, A3R with a mystery train from Wexford, and A15 with an Easter Monday special from Connolly..... so that pins it down to 12th April 1971. (jhb nerd alert)
B125 failed on the Dundalk goods on the previous Thursday and was shunted in there, remaining over easter, and being towed to Inchicore on the Tuesday.........