Can Mac OS X be installed natively on itanium EFI systems? Since both OS X and itanium uses EFI.

I doubt it. The Itanium 64-bit CPU architecture is entirely different from the x86-64 CPU architecture used by the CPUs Apple uses in its systems. It's just barely conceivable that Itanium could run a purely 32-bit version of OS X, but this seems like a stretch to me.