Free Busy question-Exchange

when this command is executed:

Add-AvailabilityAddressSpace -forestname ZimbraFQDN -accessmethod Publicfolder

does this just provide access and updates from Zimbra free busy info to the associated contact in AD that represents the Zimbra account?
I am assuming that Exchange 2010 based mailboxes will still use the availability service and their Free/Busy information is still based out of their mailbox and not in the Public Folders.

The only reason that Public Folders are required would be to contain Zimbra Free/Busy information synced from Zimbra to Exchange.

Reason for my question is the Operations group is concerned that a change from the command above will modify the way Free/Busy is handled for existing Exchange users, where if my assumption is correct, there is no change. The only change is adding in a location where Zimbra based Free/Busy can be synced to to allow Exchange users to view it.

Please comment.