"To be clear," Huber told reporters and television cameras, "this is a positive development and an agreement that not only advances the general interest of justice but also significantly benefits our continuing investigation into individual misconduct."
Huber declined to answer reporters' questions.
However, The Salt Lake Tribune has witnessed three federal prosecutors involved in the UTA investigation shuffling in and out of a grand jury meeting room at the federal courthouse during the past two weeks.
The cooperation agreement distributed to reporters Tuesday cites a 2014 report by the state's legislative auditor general.
The 2014 legislative audit found that UTA was acting as a source of funds for developers rather than a partner in what's called a Transit Oriented Development around the Draper FrontRunner station. It cited a $10 million payment from UTA in December 2009 to developer Jeff Vitek, supposedly for construction of a parking garage, although there were no immediate plans to build one. The funds were paid shortly after the developer acquired the right to purchase property at the station site, the audit said.
"The concern with UTA's financial role is consistent with our earlier observation that, in some respects, UTA seemed to be acting as a banker for the same developer with the $10 million advance payment for the Draper FrontRunner parking structure," auditors wrote.
Developers at the Draper site included at various times Terry Diehl, a member of the UTA board. A 2010 audit found that Diehl appeared to have violated conflict of interest laws by using insider information to obtain developer rights to the Draper station project.
Diehl in late 2009 supposedly sold those rights to his partner Vitek, though documents in lawsuits now in state courts say Diehl retained a 50 percent ownership.
Investigative and audit documents say Diehl "made less than $24 million" when property at the site was sold to eBay. Diehl has said most of the money was used to pay bills, and that he made "very little" profit. Auditors referred the matter to the Utah attorney general's office, which handed it off to federal prosecutors in 2013, citing a conflict of interest.
Diehl's attorney, Peter Stirba, said he had no comment about Diehl's possible role in the federal investigation.
Stirba also has been representing Utah House Speaker Greg Hughes, a former member and chairman of the UTA board. Court documents suggest that Hughes may have received hundreds of thousands of dollars from Diehl through the Draper project, though both have denied that funds were paid to Hughes, his family or related entities.
A statement provided to news organizations by Hughes' attorney Brett Parkinson said the speaker had met recently with federal authorities, but he has been informed that he was not the target of an investigation.
"I have spoken with the U.S. attorney who has confirmed to me that the speaker is not a target of this or any other investigation. Speaker Hughes has offered and continues to offer his assistance," Parkinson said. "In response to his offers of assistance, the speaker met with federal authorities last week. Out of respect for their investigation, we cannot comment further."
UTA Board Chairman Robert McKinley said the nonprosecution agreement announced Tuesday "lifts a dark cloud" from over the agency, which has agreed to hire an independent monitor to watch over its operations.
He was joined by UTA attorney Jayme Blakesley and UTA President and CEO Jerry Benson at a news conference at the agency's headquarters later Tuesday, where they outlined reforms in recent years.