To help hosting customers migrate to Exchange Server 2010 SP2, Microsoft Exchange team has published a document and a set of scripts to help in migration for those customers coming from the Microsoft Solution for Hosted Messaging and Collaboration (HMC) 4.5.
The paper is entitled "Migrating Exchange from HMC 4.5 to Exchange Server 2010 SP2."
"This file contains a white paper and PowerShell scripts to provide the recommended and supported migration path from HMC 4.5 to Microsoft Exchange Server 2010 SP2. The steps in this guide may also be helpful when migrating from non-HMC environments that have configured some form of multi-tenancy," Microsoft Exchange team stated.
The team also said that they will soon release a guide to help you migrate from Exchange /hosting mode to Exchange 2010 SP2 installed without the /hosting switch.
Download Migrating Exchange from HMC 4.5 to Exchange Server 2010 SP2 from Microsoft Download Center.