Supposedly that is one way. Right now we used by character, so while I have my main in, none of my alts are. Not a lot of people are pleased about having to give out their BNet IDs. So it is something that is under discussion.
Are there any communities set up yet horde side? Seems to just be same faction and just use an invite link, seperate from the blizzard ID communities .
“Communities you create are open to same-faction characters from any realm within your region. You’ll be able to invite characters directly, provide a code, or send an invitation link to those you would like to invite to your newly-created community. You’ll also be able to create calendar events specific to your community and use Quick Join to hop into groups together.”
There is. Check out the post in the horde section (or do what I did and just search for horde community)! https://forums.oldtimersguild.com/t/how-to-join-the-old-timers-guild-horde-in-game-community/3153
Thanks 
. Joined on my pally Tandea, look forward to maybe playing and meeting others in game since this helps join servers.