"There has been a lot of talk here lately about Bras at work.
Can anyone make a case for where a Bra could be required?"
Lingerie model. But that's probably not what you had in mind.
Competitive swimmer might count, if you consider bikini tops to be like bras, but most wear one piece suits (I understand drag from turbulance would be a problem with exposed breasts, if you're going for speed).