I'm working out and testing doing OS upgrades through Self Service with cached packages. Of course my curiosity was sparked when watching the process.
There is a first stage of the process that takes a few minutes. Is this process just creating the Recovery Partition? Is anything else happening?
I assume you are talking about the procedures outlined in http://resources.jamfsoftware.com/archive/Deploying-OS-X-v10.7-or-Later-with-the-Casper-Suite.pdf?
Lot of things happen, including creating or updating the Recovery Partition. You can look in the system.log and installer.log files in /var/log for more information.
On a tangent note, Mike Boylan wrote an excellent analysis of the InstallESD file. You can read it at https://www.afp548.com/2012/05/30/understanding-installesd-recovery-hd-internet-recovery/