I'd bet no, but I haven't used one so I don't know for sure.
For my 5D2 I use the Eg-D precision focus screen for wider aperature lenses like the 85L and I suspect that a version of that will be available for the 1Dx in time, if not immediately.
The screens don't impact autofocus at all, but they do change the visuals you'll see. The Eg-D appears at least one stop darker when looking through the viewfinder, for instance.