Wrathmonk I think that Ebola is a special case in that no civilian air ambulance services are suitably equipped to transport Ebola cases.
It is already very, very difficult for private civilian air ambulance companies to survive because of the capital cost of suitable aircraft and the paucity of their employment. Most "air ambulance" aircraft are little more than an ancient business jet with some seats removed and are completely unsuitable for transporting even a patient on a stretcher.
I do agree though that the RAF should bill for these humanitarian flights to the company or the company's insurance. I was very aggrieved in the early days of Op Ellamy when the RAF suddenly decided to fly to Libya and "rescue" stranded oil workers because the company I was flying for at the time was making a packet from doing the same work and suddenly we had the market cut from under us by the RAF who could do it for free publicity!