The Corporate Trustee assumed my liability
A Corporate Trustee is almost always a "non-discretionary" trustee. Such a corporate trustee will NOT make any investment decisions regarding the Plan's assets. It only acts upon specific instructions from the Plan Sponsor.
The Plan Sponsor has only changed the title of the person whose responsibility it is for investment oversight. Instead of Employee A of the company being the Trustee, Employee A is now the "Investment Committee," having the identical liability for investment management he would have had if he remained as Trustee. The Investment Committee instructs the non-discretionary Corporate Trustee as to which investment options are to be made available to participants and beneficiaries. All members of the Investment Committee now have the personal liability.
A Corporate Trustee's primary liability is for "ministerial mistakes," the failure to execute instructions properly. A non-discretionary trustee exercises very little independent professional decision-making for determining the course of action for special events and transactions-perhaps no more than a regular custodian and Third Party Administrator would affect.
Generally, the Corporate Trustee is also the Custodian of the Plan Assets. Ask your Corporate Trustee for a written list of what additional duties it performs as Corporate Trustee that it would not perform as a custodian.
The difference in duties might only amount to its willingness to "certify" the statements of the custodial account.
A certified statement of Plan assets will help reduce a Plan's audit costs. Many custodians will certify statements without the necessity to be the Plan's Corporate Trustee.
Some custodians will act as Corporate Trustee without additional charge from that of being a custodian.