PG&E continues to wrestle with gaps in record keeping for its vast natural gas system -- one of the factors that contributed to a fatal explosion in San Bruno -- and is attempting to cope with subsidence issues for some of its gas pipelines due to the devastating drought. The disclosures came at an extraordinary hearing held Thursday by the state Public Utilities Commission, which met with top executives of California's major utilities in an effort to pave the way for safer gas and electricity operations in the state.