Canadian Senior Captain was successful bidding last LAX bid, however didn't get the base as he is Canadian, no US visa. Basings agreement does not say anything about visa requirements for a base, only residence. As the basings agreement is part of the Canadian CBA he grieved it.
Fact is that the new CX USA is still a HKG company, a foreign entity with a US business licence. As such a Canadian can be employed with CX USA, operate foreign registered aircraft from a US base as long as that officer is a US non-resident entering on a C1/D1 visa. The I-9 is no problem in this case with proper documentation.
All these conspiracy theories that CX or the officers are breaking the law in this regard are wrong. The US immigration department, the US IRS are fully aware for many many years that all these Canadians are on US bases even before the on-shoring.