Powell did not respond to messages seeking comment.
Joe Jamail, a billionaire trial lawyer who is one of the top donors to Texas, is Brown's attorney. When asked about the conference call with Sexton and the lunch meeting, Jamail suggested Hall was acting on his own and threatened to sue anyone outside the university if they try to pressure Brown to resign.
"If there are any more, get ready for a lawsuit," Jamail said. "Mack has publicly stated he wants to coach."
After Brown and Tom Hicks spoke, Sexton was informed that Brown would not retire, Hall said Thursday. He said he has not been in further contact with Sexton and didn't know if anyone else from the university had spoken with the agent.
Hall is under impeachment investigation by the state House of Representatives and lawmakers have complained that he has tried to force out university President Bill Powers, who has been a strong advocate for Brown. Steve Hicks has been among the regents backing Powers in a public spat that has embroiled the board members and state lawmakers for more than a year.
A spokesman for Powers said the president was unaware of the call with Saban's agent or the meeting with Brown.
The conversation has been rumored for months. That a regent participated — whether on behalf of the board or on his own — underscores the pressure Brown is under to turn around his struggling program.
Texas went 69-9 from 2004-2009. But the Longhorns slid to 5-7 in 2010 before seasons of 8-5 in 2011 and 9-4 in 2012. With 19 returning starters, Brown suggested before the season that Texas was on the verge of returning to national prominence. Instead, the losses to BYU and Ole Miss have left Brown fending off questions about his future every week.
On Monday, Brown dismissed "rumors" about his job.
"They've been swirling for 16 years," Brown said.
AP Sports Writer John Zenor in Alabama contributed.