There are some guys on here who can probably go into more detail physiologically, but I would guess that the 12/14lbs that you have read about is a generalization.
That said, it is hard to put on substantial size in one area without all around training.
You could certainly emphasize your biceps in training and get them to grow faster than other body parts. Whether you would gain a full inch without adding much muscle everywhere else probably depends in large part on your routine, your genetics, etc. Either way, I suspect this would have to be a long term goal since it is so focused.
Also, don't forget that triceps are actually capable of adding more size to your arms than biceps.