If you are interested in finding a job outside of AT&T for whatever reason, is there any downside to volunteering for the MVO offer and looking around for a month? Then, if you find a job and get to leave with the severance, great! If you don't find a job then you just rescind your offer to leave by the date and time listed and stay with the company.
Yes, I know they could then have you on a list as wanting to possibly leave. Let's assume everyone is on that list for the time being.