As far as the session goes, I am not sure that you will be able to fire an event based on session timeouts. Analytics sessions time out when a user has been inactive for 30 minutes, usually because their browser has been closed. Since the browser is closed, there is no mechanism that fires an event. Its not an event that occurs, it more that it expires.
What is it that you are trying to track and achieve with this reporting? If you could provide a little more detail, then maybe we could answer your question better.
Could you please suggest on how to get mbox timeout scenario for at.js file. We have at.js ver 1.2.2, I have tried to load the same on network with speed 50kbps. We are geting mbox cookie but em-disabled#true is not setting up.