The Supreme Judicial Court is authorized to prescribe by rule or order the selection of juries from regions consisting of a single county or a reasonably compact group of counties for trials of criminal prosecutions or civil actions in the Superior Court. If the Supreme Judicial Court shall by rule provide for such regions for the purpose of selection of juries, this chapter shall be applied to such regions and to such regional juries and the word "counties" where it appears in this chapter shall be read to mean "region."   [PL 1975, c. 337, §2 (NEW).]