Always nice to hear from someone who is clue-free! Clearly you have not read the certificate of validation, issued by the CAA. It states that pilots with FAA certificates, working for Atlas Air Inc, are authorized to operate at pilots with all the authority that the FAA certificates grant them under US/FAA regulations while operating aircraft listed on schedule "A" of the certificate of validation, which lists the "G" registered aircraft which the US/FAA pilots will operate, nothing about EU licenses, nothing about right to live/work in the EU/UK. Looks like Atlas Air Inc. have bought themselves some regulatory relief from some UK ministry types. Capitalism at its finest.