>> Update to the latest scan engine (anti-virus) (is this as simple as doing updates in Symantec?)
That sounds about right. They may also verify that all client machines are running the latest definitions and engines as well
>> Update anti-virus boot disk
They probably have a bootable antivirus/rescue media to use should a machine get infected. They would make sure this media has the latest definitions
>> Perform restore of test data to all partitions (using Backup Exec 11d)
They probably take a recent backup and restore a selection of the data to a specific target folder to verify the backups are valid and working.
>> Search for breach attempts (security)
They probably comb through logs on your firewall and event viewer logs on the server to lok for multiple failed logon attempts and where they are originating
>> Verify mirror or RAID-5 is operational
If it's software RAID then I would imagine they just check within disk management or if its hardware RAID then within whatever management software it came with.
>> Do you have a recommended Server Maintenance list?
Show us what else you have on yours and we can add to it.