Quoting:
“We take seriously our obligations to follow all applicable laws, federal regulations, and Department of Justice policies when issuing subpoenas for phone records of media organisations,” the office said.
Note the weasel words ‘and justice department policy’, also note that ‘we take seriously’ doesn’t say they did have a warrant or subpoena.
I have not read anything yet that leads me to conclude they had warrants or subpoena.