Thinkprogress & TPM have this story.
If you have been following this story line from a couple weeks ago, this is the lady who held the list of the US Attorneys that ended up with pink slips then plead the fifth when told to come be testify. It has been a rollercoaster to get to this point. The committee approved immunity and then the Justice Dept authorized granting immunity.
"I believe obtaining her testimony will be a critical step in our efforts to get to the truth about the circumstances surrounding the U.S. attorney firings and possible politicization in the department's prosecutorial function," -John Conyers
I really think we have a good opportunity here, after hearing Klye Sampson and Fredo himself testify, for the committee to come away with the bigger picture more in focus... that was setting up the 2008 election for a Republican win. The axed attorneys were loyal to the law instead of the Rove agenda and tactics which are all part of a scheme to maintain Republican dominance.