There are lots of airports where AA occupies an entire terminal yet there are premium lounges. They're a great place to get away from the crowds at the gates and relax or work. Presumably, B6 could offer access to the lounge for a fee, like most airlines in the USA.

In the USA, airlines pay all the costs of the line-minders that control access to the priority security lanes. Everyone up until you get to the TSA license/passport/ID checker.

For a while, the TSA was antagonistic toward the priority lines, and proposed doing away with them, but the airlines reminded the TSA that the airlines pay the rent on the terminal floor space all the way up to the TSA document checker and the airlines paid the wages of the line minders, so controlling the lines up to the document checkers was going to be done however the airlines saw fit, including separate lines for First/Business class or Elite frequent fliers.

The airlines held fast and convinced the TSA that controlling the waiting lines to enter the checkpoint was the business of the airlines and screening the passengers once they waited in the airline-controlled lines was the business of the TSA. And the former wasn't any business of the TSA.

More recently, however, the TSA has begun to buy into the idea of priority lines - and has even set up completely separate checkpoints (with airline assistance) for Priority lanes, like for AA at LAX, where First/Business class/Elite frequent flyers now have their own separate lines and checkpoint. One unintended consequence (or perhaps intended) is that it makes it tougher for the paparazzi to harass the celebs.