Maine’s highest court has affirmed a decision that Central Maine Power’s “smart meter” system poses no credible threat to the health and safety of customers. Opponents challenged a decision by the Maine Public Utilities Commission that 600,000 smart meters installed in homes and businesses were safe. The opponents, led by Ed Friedman, say the commission’s determination wasn’t supported by enough evidence and contend that two of the commissioners gave differing rationales for their decision. The Maine Supreme Judicial Court published a decision on Tuesday that it has sided with the utilities commission.