HARRISBURG - Gov. Corbett will announce his plan Monday to expand health coverage for the poor by using public dollars to finance commercial insurance for 500,000 uninsured Pennsylvanians. Corbett, ending months of speculation about whether the state would take advantage of billions in Medicaid dollars, will seek approval from the federal government to provide private health coverage rather than expand the state's Medicaid rolls, say several people who were briefed on the plan. "Next week, the governor is going to outline his vision for a Pennsylvania-specific plan to increase access to quality and affordable health care for all Pennsylvanians," said Jennifer Branstetter, Corbett's policy secretary, who declined to give details.