They just place ads on it. Motivate runs a lot of bikes: Ford Gobike (SF), CitiBike (NYC), Biketown (Portland), Capital Bikeshare (DC), Divy (Chicago), BlueBikes (Boston), Cogo (Columbus), Nice Ride (Minneappolis),
From Wikipedia: "Named after lead sponsor Citigroup, it is operated by Motivate..."
No, they are owned and operated by Motivate. Citi has, essentially, bought ad placement - similar to putting your name on a sports arena.
To add to that it's Ford GoBike in SF - same company's.