For plastic surgery, some things are, or can be, covered - probably depending on the insurance you have, etc. I know a girl who got a medical breast reduction (for back problems) and her insurance covered it. I also know a girl whose insurance covered a nose job because something about a sports injury that broke her nose and she had difficulty breathing because of how it healed? I forget the details.
I also know women who are breast cancer survivors who had their breasts removed, and then their insurance would cover for a breast augmentation so they could have breasts if they choose to undergo the surgery. They had to go within reasonable means (same size as pre-surgery I believe) and there were limitations, but many women who had the option (who I've encountered) accept the offer.
I don't know specifics, only what people tell me from their experiences, but certain things can be covered - just a matter of getting your insurance company to agree on what's "worthwhile and necessary" and what is not.