I don't generally contribute any more, but I think this is important information.
There is a superb piece by Jens Flottau in Aviation Week for August 10, 2009 detailing what was known about high-altitude (e.g., FL 350) extra-cold (-50°C and below) pitot icing on A330/340 aircraft before June 1, 2009. The answer is: lots.
In my opinion this is prize-winning research and writing. It hasn't been mentioned here up to now,
AFAIK.
Response to Airbus Pitot Tube Incidents Under Scrutiny | AVIATION WEEK
PBL