Fifteen years after blackouts swept the state, a Federal Energy Regulatory Commission judge has found that a division of Shell Oil engaged in fraud and market manipulation during California's energy crisis, with company traders joking on tape about burning the evidence if they were ever caught. The tentative decision, which must be approved by the FERC board, holds Shell and Spanish energy company Iberdrola liable for $1.1 billion in ill-gotten profits, money that could be refunded to Californians if the decision stands.