On Jul 13, Bharat Suneja (MSFT) wrote;
Multi-Mailbox Search required an Enterprise Client Access License (CAL) for each mailbox searched. (…). Today we’re making a change to Exchange 2010 licensing so you’ll no longer require an Enterprise CAL for Multi-Mailbox Search. This is not yet appears on Exchange Server Licensing. But the MSFT mentioned that this will be updated.
This is not applied for Legal Hold or Personal Archive.