The company has been sharing information for several years now including in Los Angeles.
According to ABC News, the program, used by the FBI, Department of Homeland Security and Drug Enforcement Administration, is primarily intended to let federal agents "more efficiently" respond to lawfully obtained subpoenas and keep up with suspects who routinely swap cell phones.
Hemisphere is used mainly in high intensity drug trafficking areas like Los Angeles.
AT&T supplies customer data in real time after a subpoena or warrant is obtained.
The Los Angeles office has processed more than 4,400 requests since 2007.
ABC News contributed to this report.