The Police seem to have investigated RIPA based complaints before.
Its ridiculous the police are refusing to investigate this they must have conducted investiagations based on RIPA in the past. I seem to remember a case of some waste company that was illegally wire tapping the phones in a village near them to scupper some campaign against the company organised by the locals.
http://news.bbc.co.uk/1/hi/uk/6767019.stm