US Corporates will have to hire doctors authorised to practice by the BMA ..
Not if TTIP gets ratified the way it's currently looking. If a health care company wants to employ a doctor that they would be able to employ in the US, then the BMA would have to back down - or they and the UK Government could be sued.
Under TTIP, it matters not a jot what the government or the UK professional bodies want, they have to comply with the 'least obstructive' law. This is in the name of promoting "free trade on a level playing field".