Nintendo designed the N64 and Nintendo designed the GC so Of course, Emulation there is possible. This fact has no bearing on the probability of success of a N64 emulation on the PS2 and I don't see how it would.
I have the N64 emulator for the xbox and it runs like ass, so, being that the xbox is a little more powerful that the PS2, and given the fact that the N64 is a complicated machine to emulate, even for a nice PC, it isn't gonna happen.
Furthermore, If an N64 emulator was ever released for the PS2, it would only be a crappy, unplayable, proof of concept.
Nintendo Entertainment System - Region Free
1.1 Xbox - TSOP - 160GB - LG 8164 - HD/LAN/DVD led
1.0 Xbox - Slim - Xecuter 2.3b lite - 160GB - HD led
V7 PS2/FMCB1.7/2 Datel 16mb cards/Network Adapter