FYI, I spoke at length with someone at the immigration dept several years ago. What you say above is correct. The difference is that CX actually BASED the pilots in the US.
You spoke to someone at the Immigration Department... WOW what an expert you are! Big deal. Whether it suits your personal little backstabbing maneuver or not, the situation IS LEGAL. Many other airlines do EXACTLY the same thing as do many other industries.
and keep actual AMERICAN CITIZENS out of their own base for up to the next 20YRS!!
Do you really think you OWN the bases? It's actually none of your business what one chooses to do when they arrive at their base. I can do, and go wherever the hell I want, and I certainly don't have to justify it to you!! Again, whether you like it or not, those guys are SENIOR to you. That's the way it works.