I have heard that one of the well known 3 above has only paid out for some medical costs being claimed for (on one occasion) in the last couple of years. I believe there were other things claimed for under the insurance, but were rejected.
I believe the country was Burma and the insurer may have been Dogtag. I think the scenario was Expedition and no organised cave rescue, but a Team/self extraction was carried out.
I think I might need to read our club journal again, there might be more details in there.
The information above is third hand.