An L.A. County sheriff’s deputy patrol car at the La Mirada substation equipped with a roof-mounted system that constantly scans for and photographs the license plates of nearby cars. AdvertisementBut after a summer of ramped-up deportations, the county supervisors decided to impose more transparency on who’s requesting license plate data from the Sheriff’s Department — and when the agency provides it. U.S. Customs and Border Protection also has its own license plate readers around Southern California, he said. Maass said even if a county bars its local sheriff’s department from sharing data with ICE, it’s difficult to guarantee the rule is followed by the rank-and-file. An L.A. County Sheriff’s Department patrol car equipped with a license plate reader can scan somewhere between 1,000 and 1,500 plates a day.