Under Irish law a designated High Court judge (currently Mr. Justice Iarfhlaith O'Neill) is assigned to oversee the operation of telephone tapping and data retention. Unfortunately, the annual reports of the designated judges are not exactly models of transparency. Here's the most recent example - all three paragraphs of it:
I'll be writing more about Irish law in this area shortly: stay tuned. (Or should I say "keep listening"?)
Edited to add: The Sunday Times has now picked up on this issue.