Well the case has been going on for awhile. What's interesting is Loretta Lynch, now the US Attorney General for a month, was the US Attorney in Brooklyn and oversaw the investigation.
Switzerland’s treaty with the United States is unusual in that it gives Swiss authorities the power to refuse extradition for tax crimes, but on matters of general criminal law, the Swiss have agreed to turn people over for prosecution in American courts.
I suspect the investigation got started or got a big boost after this:
As new accounts of bribery continued to emerge — a whistleblower who worked for the Qatar bid team claimed that several African officials were paid $1.5 million each to support Qatar — FIFA in 2012 started an investigation of the bid process. It was led by a former United States attorney, Michael J. Garcia, who spent nearly two years compiling a report. That report, however, has never been made public; instead, the top judge on the ethics committee, the German Joachim Eckert, released a summary of the report. In it, he declared that while violations of the code of ethics had occurred, they had not affected the integrity of the vote.
Within hours, Garcia had criticised Eckert’s summary as incorrect and incomplete, charging that it contained “numerous materially incomplete and erroneous representations of the facts.” Nonetheless, FIFA moved quickly to embrace the report’s absolution of the bid process. Qatar World Cup officials said the review had upheld “the integrity and quality of our bid,” And Russia’s sports minister, Vitaly Mutko, told reporters, “I hope we will not have talk about this again.”
I would think you could subpoena the report from Garcia who would have benn happy to fork it over.