You guys are misinterpreting this. It's not 12 cameras, it's 12 setups. A setup is just that, meaning the camera and lighting is setup for one specific angle. When you change angles, you have to move the camera, move the lights, fly in or out parts of the set, etc., and set it all up again.
The article says they were only shooting 3 setups in a single day, rather than the 12-15 expected.
Oh, interesting! Thank you for the correction, I'm not usually very well aware of the day to day practicalities of a film-set and the related terminology.