Does sound pretty preposterous. Next it'll be plastic surgery!
I have wondered though - if you're in the prison system, and are independently wealthy, can you choose your own healthcare? I imagine most guys with long sentences don't have health insurance and can't really afford to pay (heck, most people would have a hard time completely for their own healthcare, inmate or not) so they just see the prison doctor. But if you are wealthy - like a mobster or white-collar corporate criminal - can you see whomever you want and get whatever treatements, therapies, etc. that you want?
It seems like a sticky situation - allowing it could lead to abuse, but if you deny the absolute latest and greatest care to someone, I could see them suing the prison system for damage to their health - unfair deprival of life, liberty, and happiness. Then again, if you could afford the legal power to win such a case, you probably don't end up in prison in the first place!
Just rambling.