I read that article a bit more closely, and the tests only say cell phone use
may cause interference. Even then, it only affects the plane's systems when the cell phone is used near the flight deck or the avionics bay.
Dan Hawkes, head of the avionics section of the CAA's safety regulation group said: "The tests showed that a mobile phone used near an aircraft's flight deck or avionics equipment bay will produce interference."
To me, that means that there is no proven risk, especially if you're not on the flight deck. This is like the often-told, but never-proven tale that cell phones cause cancer.
However, an airline is certainly within its rights to ban cell phone use to prevent even the *risk* of interference. I just don't think we have scientific evidence.