Bill,

I believe that most NDA's have within them certain exceptions carved out to the otherwise strict confidentiality.  For example, if a court orders you to disclose, you need to disclose; and that disclosure may well be just to the judge and not presented in open court, or otherwise in pleadings, depos, etc. 

Some confidentiality agreements would have a carve out for matters to be disclosed to a prospective acquirer, so long as the contents is kept very much under wraps, those that are allowed to review it sign appropriate confidentiality agreements and containing stiff financial consequences for breaching that confidentiality.  

I believe that before any acquisition (or other really significant event), the share price will do a little something; our has done nothing. Once in a while, the good news really does come out of the blue and takes every non-insider by surprise, but that's the exception.  The problem is that while most great impending things are reflected in the share price, not every time the share price makes a move that may signal something good (or bad) coming, does it really happen.  I'd say over half the time, it's a false alarm.