Blue Cross and Blue Shield says it has reinstated health coverage for thousands of stranded customers who were dropped from the insurer's rolls in a technology debacle that cut off coverage for residents with urgent medical needs and rippled throughout the state. But the state's largest health insurer is not disclosing how many customers are still without health insurance, even as Blue Cross concedes that call volumes to the company's help line remain far above normal. Both the N.C. Department of Insurance and the N.C. Attorney General plan to review the episode, the most serious crisis in Blue Cross's recent history, after immediate customer needs have been resolved.