Mass. Gen. Laws ch. 79 § 44
If the agents of the United States and the persons owning or interested in any property which is required for any purposes for which the United States is authorized to take property by eminent domain cannot agree upon the price to be paid for the interest of such persons therein, the United States may file a petition in the superior court for the county in which such property lies, praying for the condemnation of such property. Such petition shall contain a description of the property to which it relates, sufficiently accurate for identification, and a statement of the purpose for which it is sought to be taken. If the court, after notice to all parties interested, finds that the United States has the right to take such property by eminent domain, it shall determine the value thereof in accordance with this chapter, so far as it is applicable. If such value with costs and reasonable expenses to be taxed by the court is, within thirty days after final determination thereof, paid or tendered to said owners or parties interested, or in case of their neglect or refusal to receive the same, if it is paid to the commonwealth for their use and subject to their order, a decree of condemnation shall be entered by the court, and, if the property taken consists of real estate, a copy of the decree shall be recorded in the registry of deeds of every county or district in which said property or any of it lies, and the fee of said property shall thereupon vest in the United States.
Mass. Gen. Laws ch. 79, § 44