The process requires that the PST Export and Import wizards be run. The process is not automated as far as a scheduled Task is concerend though the wizard does automate the import of the PST into an existing archive.
When you export archives to PST files, a configuration file is automatically created for each PST file. This configuration file contains information that is needed if you intend to import the PST file contents back into Enterprise Vault,including:
■ The retention category that was applied to all the items in the PST file
■ The Vault ID, which is needed to correct shortcuts that have been broken by the move
This information can be found in the Administrator's Guide page 204 (Moving a mailbox)
ftp://exftpp.symantec.com/pub/support/products/Exchange_Mailbox_Archiving_Unit/289858.pdf