Hi
"Although I checked my network share and there doesn't seem to be any files from my current home drive there?"
That's because the user who logs in has to specify what Sync Preferences he/she wants. The AD Plug-in does not do this automatically.
"How often does it actually do the backup to it?"
Explore the settings in the Accounts Preferences Pane for that User once he/she has logged in and you'll see what options there are. If OSX Server is in the mix you can define sync preferences from there. Otherwise it's purely User driven.
"Is there a attribute from AD that it uses to detect the home drive?"
Yes. This has already been pre-mapped for you by Apple and is part of what you get when using the AD plug-in. To see what attribute this is launch Terminal on any client that is bound to AD and use dscl to 'read' what's being accessed from Active Directory. Assuming default settings something like:
dscl /Active Directory/All Domains -read /Users/nameofuser
I'm not connected to an AD at the moment but the above should work? IIRC you're looking for SMBHome or something similar. Assuming you know what to expect from AD it should be obvious to you? All of this assumes a fairly out-of-the-box AD and Microsoft's 'Best Practices for AD' and the Home Folder has been specified in the UNC path for that User's Profile in Active Directory.
You're not limited to using the AD plug-in if you don't want to? You can modify and extend the AD Schema itself and map as many attributes and values as you see fit. Assuming this is something you want to do Apple have made available a Technical White Paper outlining what needs to be done.
You may find these useful?
http://www.inspirednetworks.ca/site/wp-content/uploads/2009/08/Modifying_the_Act ive_Directory_Schema.pdf
http://www.seminars.apple.com/contactme/pdf/L334436B_ActiveDirect_WP.pdf
There is of course far more than what Microsoft and Apple provide themselves. There are some extremely good - but expensive - 3rd-Party products that make a lot of this easier and more seamless for IT Departments and Users wishing to integrate the platform into AD.
HTH?
Tony