I had an Ivy league university ask about this. There is a way to do this documented below:
General split permission model - http://technet.microsoft.com/en-us/library/aa996881(EXCHG.80).aspx.
UM Split Permission model - http://technet.microsoft.com/en-us/library/bb266903(EXCHG.80).aspx
They also had a specific question around delegating the Auto Attendant wave files. Here is a potential workaround:
You can re-record UM custom prompts (Dial Plan and/or Auto Attendant) over the phone, i.e. by calling in to the system.
So it might be easier to accommodate the “low privilege UM prompt admin” role by doing the following:
1. Create a domain account (e.g. CONTOSO\umpromptadmin)
2. Disable the ability for the account to log in interactively
3. Make the account an Exchange org admin
4. Create a mailbox for the account and UM enable it
5. Give the prompt administrators the pilot number, extension number and PIN they need to log in to change prompts
Lack of interactive login means they’ll never get to run EMC or Exchange Management Shell – only use the TUI to rerecord the prompts.
There are some upcoming administration delegation changes in Exchange14 that we can blog in a few weeks that help with these scenarios.
I had an Ivy league university ask about this.  There is a way to do this documented below: