Firefox is it's own beast, it isn't tied to Windows, Microsoft, Active Directory or anything, it is free-roaming. That is why so many people like it, because "it isn't Microsoft", but that is also the reason why it hasn't many much headway at all into the Corporate world yet. The standard install does not support Windows Authentication, doesn't pull setting from Active Directory Group Policies, doesn't play well at all with others. It is pretty much a stand-alone program, so the Corporate world is mostly avoiding it.
That being said, I did hear mention of some third-party plug-ins for Firefox that allow it to be configured via Group Policy, and also supporting Windows Authentication. I do not recall the names of those plug-ins right now, but a quick Internet search will probably get you going in the right direction.
As with most things with Firefox though, you get what you paid for, and seeing as it is free you don't get much. Simply put, I wouldn't rely upon it for mission-critical applications, it is much too buggy for my tastes.