Next month, the Maryland Public Service Commission will vote on whether to allow a Canadian energy company to buy Washington Gas and Light, a public utility that has provided electricity and natural gas to customers in the District of Columbia and Maryland suburbs for more than a century.The proposed merger of AltaGas and Washington Gas is part of a trend across the country. Increasing numbers of locally-owned and controlled public utilities are being bought up by large corporate conglomerates based in distant headquarters, according to Paul Patterson, a utility industry analyst at Glenrock Associates in New York...