Read a few stories, there were ten actual arrests, which all appear to be of staff, not customers, and two customers were questioned on suspicion of engaging in obscenity, but subsequently released.
Historically, the only arrests that have "stuck" when it came to happening bars have been when the venues paid porn stars and the like to attend and engage in adult activities, or when paid staff have joined in the fun. As long as the only people screwing are unpaid (or paid to enter), the general legal consensus has been that no laws are being broken.
This time the arrests were for providing a venue allowing obscene acts to be viewed, the issue seems to center around the one way mirror used on one of the walls, which may give them the argument that the frolickers were unaware that they were being viewed. My guess would be that the charges won't stick.