What you need to be sure about, Pace, is whether a specific accident (allegedly attributed to the usage of the IMCR) was caused specifically by the IMCR i.e. was the pilot doing something which he would not have done had he had the full IR training.
The circumstances must not involve illegality, because anybody can do that. They also must not involve a pilot error other than one caused by a lack of specific theoretical knowledge which would have been rectified by the full JAA IR ground school. Being a "cowboy" doesn't count either because aviation is packed with those types, carrying all kinds of paperwork.
All in all, it is pretty damn difficult to work out what kind of circumstances would give rise to such an accident.
At a Feb 08 presentation I went to, the CAA stated they can find just one fatal accident where the pilot died while exercising his IMCR privileges. I don't know how that was arrived at but it is probably about right.
The legal privileges are very close to the full IR, and the rest is currency, currency, currency on type, money, more money, and being generally careful.