Three of Las Vegas’s largest casino operators are a step closer to firing Warren Buffett’s utility as their electricity provider — if they’re willing to pay the price. MGM Resorts International, Las Vegas Sands Corp. and Wynn Las Vegas won initial regulatory approval to stop buying power from NV Energy, a Nevada utility owned by Buffett’s Berkshire Hathaway Inc. In draft orders published Wednesday, the state’s Public Utilities Commission laid out conditions for the gaming companies to seek cheaper electricity from other sources, including combined impact fees of almost $127 million.