Re: what nut material do they use for the prestige guitars?
If it's not a guitar with a locking system, most of them would most likely have a plastic nut, but ever since Ibanez came out with thier Ivorex nuts for their acoustics I've come across an Ibanez Prestige electric with a similar material nut. (Ivorex is man made Ivory much like TUSQ, but when you compare them TUSQ is still a denser material and has a more glass like chime when you do the drop test, still it's better than plastic).
I don't think you'll come across an Ibanez with a bone or Tusq nut. Usually it'll be plastic or some really cheap graphite(and like I said.. maybe Ibanez is starting to use thier Ivorex nuts, but I seriously doubt it). Either way, I'd still suggest swapping it out for something better.