Answer:
No.
An administrator or other personal representative of an estate is a court-appointed fiduciary. He or she can hire agents to perform specific services, but absolutely cannot delegate their overall responsibility to anyone else. If a second signatory is needed on the account for any reason, the court will appoint an additional personal representative.
If a personal representative is incapacitated and has an attorney-in-fact acting on his personal behalf, then the court will appoint a new personal representative.