According to the Game Plan excerpt, he had conversations with Edwards about a donor paying for Rielle's campaign web videos.

For months, [campaign manager Nick Baldick] used the project’s enormous price tag as a reason to resist signing her contract. But eventually, a big check came in from one of Edwards’s donors, and that gave John his trump card. “Now Nick can’t tell me no,” he said to Brumberger triumphantly.

This ABC News article from January, 2011, describes the source of payments to Hunter, Baldick's connection and what Edwards' then lawyer, James Cooney said about them.

Federal records show the One America Committee paid Midline Groove more than $100,000 for producing Internet videos. Cooney said the nonprofit paid the firm a similar amount. Edwards did not sign the agreements, but they were reviewed by appropriate personnel at both organizations, Cooney said.

Rielle took issue with Brumberger's description of her when she came over to his and Edwards' table at the Regency, as published in Game Plan:

She looked like a hybrid of Stevie Nicks and Lucinda Williams, in an outfit more suitable for a Grateful Dead concert than an evening at the Regency.

Rielle responded:

In reality, I was wearing a black TSE cashmere sweater, a Kenneth Cole suede jacket, and jeans. But in his mind, I’m dressed to go to a Grateful Dead concert. Total projection!”

Hopefully the Government is calling him for something substantive related to the charges, and not just to describe "When Harry Met Sally."