I think this is more a question that you should ask the person who wrote the law. That is why every law must have it's interpretation (there special circumstances can be explained also). That's why (at least here) we have numerous books explaining in detail every single law - so it's not to be freely interpreted by a layer (who off course would only try to deffend his client). The person(s) who wrote the law know(s) best what the law was ment for and should explain it.
But what are the special circumstances?
If a woman is pregnant and the husband takes her to the hospital, but accidentaly causes an crash (because he was speeding) - what would happen?
If he had called an ambulance - it would have a siren and light - so people would know it's an emergency and would move out of the way. But since the husband drove a civil car - others had no way of knowing - and the fault would be his. So he should not be allowed to speed. He probably wouldn't get a ticket just for speeding though (even if the speeding tickets are ment to calm down the fast drivers, who are a hazard on the road).
It's just a thought though.
EDIT: Great thread though!
k: