if these rumors are unstoppable, why do you suppose potential clients bother having us all sign an NDA?
The NDA gives them recourse if a bidder not selected decides to do something silly because they didn't get the job. It's not perfect by any means, but from the money side of the fence, it's the best they can do.
Of course, if one were truly motivated to do so, one could let the cat out of the bag and probably get away with it. The NDA simply gives those receiving the information additional incentive (beyond general professionalism) to stay quiet.
The problem with any NDA is that typically far more people end up with the information than have actually signed an NDA. And the info is valuable- even if only to give someone a feeling that he has some inside scoop on something. As such, word tends to leak out.
Finally, as someone with absolutely no inside information on the golf industry of any kind- if the Hanse project in question is in any way related to one of the top dozen or so topics on this board currently- it might be the world's worst kept secret.