Ohhh, I'm afraid I don't know... But I would really like to know, so I'll keep an eye out for those magicians. I never had a lot of luck with the rare NPCs - I've only seen a (base game) magician once, and a Science Geek never. Which is sad, because I love geeks.
My guess is that no, they would not keep their jobs, because they never had jobs in the first place - like, if you marry a NPC firefighter, they don't automatically have a job when they move in. The coding wasn't there in the base game, and updating it would produce a pretty minor effect, and take quite a lot of hassle in development. That is my guess, anyway.