According to JDN (journal du net), the UK policy to intercept communications is not unique in Europe. Already, France and Germany allow so. The framework in which those "hacks" are conducted is no clearer whichever side of the Channel.
"La police anglaise s'apprête à réaliser des intrusions informatiques" (JDN, 6 January 2006) (English police ready to intrude/hack into computers)
I would argue that the practice is probably done in the open rather than secretly, although the lack of serious constraints does not give much more transparency to the persons subjected to it, whether criminal or not. And that is scary.