As much as it gins up page views, denial of access isn't proof of existence (you know once you are citing X-Files as your proof, you've gone off the deep end). I can easily see denying a FOI request on the grounds of "could reasonably be expected to interfere with law enforcement proceedings" as a simple rubber stamp way of avoiding to have go through the process of looking for the information that may not even exist. Not that it is less alarming, but I hate hazy conjecture boldly presented as fact.