I can't point you to any code, but I'll share how we differentiate between these types of accounts. Generally, addding an ITF designation with a beneficiary does not change the ownership of the account. The grantor is still the owner, and can change/revoke the trust at any time.
Listing a non-owner trustee is something we do less frequently. (Burial reserves, for example.) We use this in instances when the trustee is not the grantor.
In either instance, for CIP, we refer back to the 'person that establishes the account' rule, generally the trustee. The beneficiary, IMO, almost never meets the CIP definition of customer.
On a side note, what operational snags are you running into with your teller system?