There are many many factors involved in a friendly fire accident. There's the applicability of ROE and how it was followed. There's intel and info. . . i.e. were the flight told about live-fire exercises in the area. Generally, though, there's plenty of blame for everybody . . . Leadership, supervision, operators, etc.
With the weapons being so deadly, immediate, and long-ranged, it's even more important than ever for there to be good IFF methods or devices. Remember during the Gulf War when a small unit of Brits in an APC got fired upon by U.S. helos.
Multi-national operations make it even more likely to happen. I know the polictical reasons for the Canadians being in the AOR, but it's hard to comprehend the military ones.
Unfortunately military inquests are subject to high degrees of tampering from politicians, especially when other nations are involved.