For at least six years, law enforcement officials working on a counternarcotics program have had routine access, using subpoenas, to an enormous AT&T database that contains the records of decades of Americans’ phone calls — parallel to but covering a far longer time than the National Security Agency’s hotly disputed collection of phone call logs. The Hemisphere Project, a partnership between federal and local drug officials and AT&T that has not previously been reported, involves an extremely close association between the government and the telecommunications giant. The government pays AT&T to place its employees in drug-fighting units around the country. Those employees sit alongside Drug Enforcement Administration agents and local detectives and supply them with the phone data from as far back as 1987.