Malkav
I have no idea where the talk of artists who are endorsed getting secret "super" guitars comes from, the guys on Ibanez's roster who have signatures do end up with off the shelf models - They have an LACS custom shop, but those models are always distinct and are serialed as being such, a large amount of what the LACS turns out isn't necessarily all that custom either they mainly just do refinishes and personalised electronics configurations on their production line guitars. Paul Gilbert has been seen touring lately with his CHINESE made Fireman guitars, surely he could get a fancier guitar if that one wasn't up to his spec? As a truly advanced player I'm fairly certain his requirements would also be a lot more particular.
The artist signature Ibanez guitars don't come from the same factory as the prestiges mind you, however they are the ones you can buy if you're willing to drop the cash on them. I can't remember the name of the factory off hand, but I know it begins with an S (Sobuo?), the prestiges are from the Fujigen Gakki factory.