Advanced Teleporter NPC Lua Scripting

Ok, I have a working LUA teleporter, but I want to be able to restrict certain locations to only alliance/horde (such as alliance/horde main cities) and certain other areas to only specific levels/classes (such as shattrath, dalaran, death knight start) but I can not find any other lua teleporter npc that has these checks in them already (so I can see how it's done) or I can't find anybody releasing anything like that... I know all I'd have to do is check race or faction... What I did was make 2 separate teleporter npc's for each faction thinking I could restrict access to the npc itself based on faction but certain areas need to have both spawned next to eachother (such as shattrath, dalaran, the great arena, dk start) and they attack eachother (unless I set their faction to 35)... it would be good if I could check by race or faction at the beginning of the lua to check for races or factions before or else end, if anybody knows what i'm talking about that would be sweet
also, I know the shattrath portal gameobjects do it somehow, but I don't know if you can do the same thing with npcs, or if you can link a lua script to a game object instead of an npc...

im looking for same thing.. been testing various progs for this