Because the results of any negotiations on economic and job-protection issues (ie. money and scope) can lead to changes in the Company's stock performance, it is a requirement to sign NDA's that would prevent insider trading or other other potentially illegal scenarios.

On top of that, there are committee of the MEC that do receive confidential information from the company (routes, a/c orders, market projections) that the MEC uses to enforce applicable sections of the PWA.

I prefer having the Company's internal data plus less accurate external data to derive compliance and enforcement, wouldn't you?