Hi Karen, I have this too, our Comms department send out emails to all the staff like this too. It must have been an HR operational decision though - I still think you ought to let someone know. Do you have a dedicated HR person you could email, cc to your boss? (BTW how did you find out in the end?!)
Some of my colleagues are going through this downsizing at the moment, I'm public sector too, 10 people applying for 7 jobs in one instance - I can only hope that it will be fair.