Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 79, § 26

If a person having an interest in such property is, by reason of legal disability, incapable of choosing a trustee, or is unascertained or not in being, or if the parties cannot agree upon a choice, the probate court of the county in which the property is situated shall, upon application of the board of officers of the body politic or corporate whose duty it is to award the damages, or of any person interested or of any other person, acting in behalf of such persons, whether in being or not, as may by any possibility be or become interested in said property, appoint a trustee, who shall give to the judge of probate a bond with such sureties and in such sum as the judge may order, conditioned for the faithful performance of his duties.