CRA indicates that the trustee fees of a lawyer who was appointed for personal reasons are subject to employee source deductions

In response to a question as to whether trustee fees earned from an estate by a lawyer, who normally didn’t do that sort of work but was appointed because the deceased trusted him, were income from an office (subject to source deductions and an estate T4 reporting obligation) or from a business (subject to a T4A reporting obligation and to HST), CRA stated that the fees could be considered income from an office, if "the lawyer was appointed on personal grounds; for example, because he or she was a friend of the deceased."

Neal Armstrong. Summary of 16 March 2015 T.I. 2014-0521791E5 under s. 248(1) – office.