The NSA and US DEA trick contractors working for the Bahamian phone companies into letting them record the full audio of every call placed in the Bahamas, according to newly published Snowden leaks released in an article in The Intercept. The NSA exploits the "lawful interception" system for conducting wiretaps without having to notify phone companies in order to harvest the full run of cellular calls, apparently as an engineering proof-of-concept in order to scale the program up to larger nations. The Bahamas is an ally of the US, identified by the State Department to be a "stable democracy that shares democratic principles, personal freedoms, and rule of law with the United States."
It's not clear whether the DEA conducts "parallel construction" with the NSA intelligence (this is when the DEA overtly takes a warrant to get intelligence it already has through an NSA covert operation). The phone calls are intercepted through two NSA programs: MYSTIC (which conducts analysis) and SOMALGET (which intercepts and stores the calls). These programs are used to capture the full audio of all cellular calls in another unnamed country, and are used to analyze metadata in the Philippines, Mexico and Kenya.
The NSA documents reveal that the intelligence gathered in the Bahamas did not focus on money-launderers and tax-haven banks -- rather, they are mostly used to catch drug traffickers.