I have just taken on essentially one network, which provides for two independent companies. SBS 2008 Standard is the only Server with all AD Objects currently in same OUs - there are no conflicts of names until now.
Two Email Policies are in effect which manages the email domain side of things and filters on Organisation.
Company1 have a shared mailbox called 'admin', but Company2 also want the same. I can simply change the name to 'Company1 Admin' and 'Company2 Admin' and then modify the email addresses per policies above, but this seems a bit long winded.
I have not had to consider multiple companies under one AD tree before so looking for some hand holding/guidance.