I'm a SIRI shareholder. I'd better go demand that they release all the
engineering data so I can do my own independent analysis.
OK, I know you meant this to be sarcastic, but exactly that might happen.
It's called the "discovery process", and if either side decides to take the other to court, they will be able to get the court to order the other side to produce evidence. To the extent that the evidence can not be shared with the public, the case may be sealed so that outsiders don't see it, but the court will see it, as will the opposing sides. The order of the court for the parties to keep it secret is stronger than an NDA, and can be enforced with jail time.
This process is also available to stockholders who choose to sue, but these are either ones who hold lots of stock, or the evidence is restricted to the attorneys and a small party while they represent a larger class of stockholders.
It is also probable that for a $220M insurance policy, that there are terms regarding visibility already written into the contract, and thus this may happen without a court order. Indeed, for that much, the insurance company may even have had its own experts and inspectors in the loop before and during the launch.
So, what about AMSAT? It's a non-profit and the members own it, and they don't have the proprietary reasons of Sirius to limit visibility.
Bruce