An operational safety case will require thought and input from many 'operational' people unused to having to justify why what they do is safe. So, they'll need some training first.
While the upcoming targets are numerical, it will be harder to provide a quantitative answer to the probability of 'hazardous situation x' occurring, but a qualitative argument of a ball-park figure will go some way. Then, a reasoned, compelling argument as to why the risks associated with 'x' have been mitigated will be needed.
Biggest problem will be the cultural change in having to think hard about these things and produce an acceptable argument. (not that I'm suggesting that the risks aren't thought about now, just that it isn't all joined up)
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