Presumably, the Q&A session will only be about the scientific matters discussed in the presentations. They won't answer questions about investigative or prosecutorial aspects of the case.
What bothers me is that, if there are a hundred reporters present, we're likely to get a hundred different points of view of what was said.
Greg Greenwald, “Doubts over the anthrax case intensify — except among much of the media,” Aug. 18, 2008
http://www.salon.com/opinion/greenwald/2008/08/18/anthrax/
“FBI Agrees To Release More Details From Anthrax Probe, Backpeddles On Key Elements,” August 18, 2008
http://tpmmuckraker.talkingpointsmemo.com/2008/08/fbi_agrees_to_release.php