Zoner
The case you have mentioned is exactly the problem why there is no "outsourcing" exist in certain areas.
How private-own equipment, registered in the state "A", crewed by civilian crews, citizens of the state "A", would be allowed to participate in real war between states "B" and "C" on behalf of state "B" for example?
It is 100% useless to have eqipment available for training purposes while you know it wouldn't be available for the real job on the day "X".