Yep, you got it there at the end.
You have one CARP VIP that has the VHID - announcements happen there, and the other IP Alias type VIPs sit on top of that CARP VIP.
They all fail in a group with the CARP VIP. Actually faster than they would individually because they don't need <x>advertisements per second, where <x>is your number of IPs, just the one of the CARP VIP.
Less headache, less VHIDs, less network traffic. It's a very nice way to do it.</x></x>