Yes it is. You can see it (and extract it) if you look at a .backup in the policyViewer tool.
However, it will only restore to the same machine it was backed up on. It is keyed to only restore to the machine with the same UUID on the motherboard.
A backup from a machine in a cluster contains all the configuration information for all machines in the cluster. So you theoretically only need to make backup on one machine of the cluster and not all of them.
One last thing on the subject. If I create new or alter the existing block pages are these changes backed up and are they replicated via central managment?
Scratch that part. I just altered a custom block page i created and then backed it up and restored to another proxy and the custom page and the change where part of the restore. Much better than V6
Right. The error_template/ folder is stored in the .backup file.
As you discovered, it should restore.
I still cannot remember if it replicates in Central Management. I always have to test that out to remind myself. If you can test that, post it here so I can google it next time