can this be done for 2 tenants with PRI DID?

Yes, just set up seperate ARS tables for each company, so they push their own CID.

The big thing is to get the provider to change the name when they see the "other" company's outgoing CID number. I have done it, but the sales people at the LEC are usually stupid.

As long as you are installing new IP500, on newer sodtware, you can have 1 external MOH, and 3 internal .wav files. This is set by the incoming call route, so each companies MOH can follow the caller throught the system.

I think that the question centered around Music on hold, not Caller ID...

You CAN associate a music source with an incoming call route - so one tenant could use the on-board .wav file version and the other tenant could use the physical input source.
Mike