I suspect the one still living is very old now, and most probably no longer in the UK,
As the "IRA" authorised him to give the names I suspect they know the likelyhood of the one still living being found is slim. Without doubt he would have been told in advance his name was going to be released and to take appropriate action.
the IRa were given immunity / pardon (not quite sure of the correct term) as part of the peace talks. Why this was not applied to service men I don't know. Atrocities were committed by both sides, it was a 'dirty' fight!