i've had a friend roll up a ftp (evil) toon, and I called up my conj so i could group with him and call him into a (good) gulld hall without being killed by the guards. When we are in different zones, the F2 option wasnt working to select him, so I couldnt use COH. Its only when i went to his zone, and his name is no longer greyed out in the group window, that f2 was working, and I was able to call him to me. The bloke was only l8, and i mentored him so I'm now l8. But I dont think thats the issue - especially since I could use COH when we were in the same zone. He decided to call it a night before I started playing around with macros, but I'm curious why F2 wasnt working on a toon in another zone.
COH is same zone only, it requires you to target the player to cast. The only ways to call someone NOT in the same zone is Call of the Veteran, and (I THINK) if you happened to still have a Refer A Friend account, it used to be one of the perks to be able to port to your friend (and vice versa, much like COV does now).