Not quite digging up, but various asbestos-contaminated NIR (and some CIÉ) stock was dumped in a flooded quarry at Crosshill, near Crumlin in County Antrim, in the 1980s. The quarry was then drained and the vehicles recovered, crushed (according to some sources) and buried encapsulated in clay on the same site in the early 21st century. Apparently the move was triggered by the vehicles being "unintentionally exposed" while partially draining the quarry, see
https://www.europarl.europa.eu/meetdocs/2004_2009/documents/lt/645/645836/645836en.pdf. (There's an old thread on Crosshill Quarry
here, but it doesn't discuss events subsequent to the initial dumping.)