This is a two part question.
First: Does the IOS version of WotL support online multi-player rendezvous?
Second: If there is online rendezvous, is there a way for me to transfer my save data from a modded psVita to an Iphone?
My friend and I are trying to play the rendezvous mission (I have the Vita, he has the PSTV), and I figured if this was possible, it would be a lot easier for us to do this.
There's no online version of Rendezvous, period. There are ways to fake it and bridge that gap, though.
The mobile and PSX versions have no multiplayer whatsoever.
No, you can't transfer your save across different versions.