By Jonathan Stempel (Reuters) -A utility owned by Warren Buffett's Berkshire Hathaway warned on Monday it could face strained liquidity and lose its investment-grade status after a judge sped up the pace of trials over the 2020 Labor Day weekend wildfires in Oregon. PacifiCorp has already set aside $2.85 billion, including$100 million in the third quarter, for lawsuits seeking $55 billion over the burning of more than 2,000 structures and 500,000 acres in Oregon and northern California. Victims blaming ...