If the Irrevocable Trust is the customer for CIP purposes, do you need to obtain CIP information on the beneficiaries only? Or, do you need to do CIP on the deceased Grantor? Thanks.

You perform CIP on the Trust. An Irrev Trust will have an EIN.

What about the Trustees of the Trust?

If your bank's CIP calls for obtaining and verifying ID info on the trustees, yes.

FWIW, because trusts themselves are so easy to fake, verification of their "identity" doesn't give me warm fuzzies. I'd always want to know about the trustees.

I personally think that verifying trustees is a reasonable KYC step and should be a standard practice when establishing a trust. Depending on the nature of the trust, verification of beneficiaries is also important to understand the ultimate beneficiaries of transactions. You might classify it more under CDD than CIP.