A group of 477 individuals costs The City more than $20 million in emergency medical services in one year — 10 of whom racked up ambulance, emergency, detox and crisis psychiatric services to the tune of $2.3 million. Those figures have been compiled as part of a new Department of Public Health initiative to get a better handle on San Francisco’s most hardcore homeless population — individuals dubbed “high users of multiple systems” who in many cases suffer from debilitating psychiatric or medical diseases, and typically have severe dependence on alcohol or drugs.The information about this population was unavailable until...