During season 1 of Beta, I asked in the forums about this and Norbert said it was man coverage. I would dig up the post, but Beta forum only has 3 pages right now and all the posts are current. In his response, he went on to describe how there were exceptions, and/or how it was man in paticular zones, and the definitive answer concerning man/zone was sort of lost, at least for me anyway. He never gave a clear answer about safeties, but I am pretty sure linebackers can be assigned to cover certain players, although Harris may be right about how that works concerning the depth of the opposing teams play regarding that player.
I am pretty sure Oriole changed some things regarding coverage since the "triple coverage/ DBs are everywhere" issue was eventually improved upon when he took over for Norbert a few seasons into Beta. Hopefully he can give a definitive answer because I am curious about this too!