Well, unless im mistaking what you are asking (Possible
) who's zone it is doesnt really matter.
By going on the Group Finder, you are asking the game to find 3 other people to do a FP with, and everyone would have done the same thing as you by going into the queue also. By everyone accepting the invite, you all get the same quest, so thats why who's zone it is doesnt really matter.
It is possible to put together a team before using the finder also, and the finder will just fill the remaining spots in the team using random people that have queued. So if you have a Healer friend for instance, and you are a Tank, the Group finder will get 2 random DPS from the finder.
Hope that helps you out