can you join in bg's with people from diffrent realms

i have a friend oon terokkar but im on azjol-nerub i have their real id and i know bg's can be with people from diffrent realms but can it be a spesific person?

 

Unfortunately you can't =/.

Your best bet is for both of you to hit the queue button at the same time and if the queue pops up ask if the other person got a queue at the same time, if they did it's likely you'll be put in the same bg.