Based on the fundamental principle of freedom of speech Brian or anyone that gets terminated or let go has the right to discuss it in private or public. Without a contract with a confidentiality agreement Brian has every right to speak out.
This ATS "cones of silence" style of managegment is totally alien to me. Sure Nazis and Commies could enforce such laws - but not in Canada and most other countries that have respect for their citizens.
If ATS thinks Brian broke laws by discussing his firing or by mentioning Yuna's new LP music they can "level of management" him. But realistically that would bring more bad publicity and most likely raise the profile of this messy split to the realms of Late night one-liners and SNL skits.
I doubt ATS wants that but they are free to try if they think it will make things better for them.
I can see Letterman with a "Top 10" list of reasons that Yuna left Brian. Or better yet how about Tina Fey with a little make-up doing to Yuna what she has done to Sarah Palin.
Yum, yum