I don't have the book right at hand, but as I recall, Thomas made it quite clear that Dr. Cameron was valuable to the CIA precisely because he was Canadian -- an American doctor would be more closely scrutinized, more vulnerable to exposure.
Also as I recall, Dr. Cameron was quite vigorous about his business. He was not a tool to be deceived or coerced by American spooks. He did what he did of his own active volition.
His two lab assistants -- they were the super-creeps, the Igor assistants to Herr Doktor. The ones who spent a lot of time with patients, carrying out the doctor's orders, and whatever: drugging patients into comas, shocking patients into comas, drugging patients out of comas, making patients wear headphones repeating short loops of their own voices, over and over for hours ("psychic driving").
Of course, for "patients" read "torture victims".
Christ, what a world we live in.