Basically you win trade pvp pet battles - the queued pet battles, not dueling.however they haven't fully taken advantage of how easy this is to level pets (and with 5.2 get a lot of lesser charms, and a little nerfed xp). I've been successfully using this method since last year to level pets very quickly.
The trick is WoW will try to match you up with another person who has pets within 2 ranges of yours. This gap doesn't increase as time goes on so if you're queuing with pets that aren't all level 25s you may actually never get a battle with anyone. So if two people queue with two level 25 pets and a level 1, for example, it is almost impossible to come up against others. This does fall down a bit as your pets get to around level 25 as you'll start getting other people and it's doubly annoying because when you decline the queue the other person remains in it. However if there aren't many people queuing it is entirely possible to level a pet from 1-25 in under 20 minutes. I do expect this to change as more people catch on, though.
Getting into the meat of this, here's an addon I wrote which will communicate with another person and queue at the same time with the same level pets. For this to work well you will obviously need two accounts (or a friend) and have a decent spread of pet levels. The safari hat also helps. After editing a few variables at the top of the file, the addon will do everything for you except forfeit battles as that is (currently) the only LUA protected function. With an autoclicker or lua unlocker you can 100% afk this.
Download here: --> "http://pastebin.com/gmBeEgD6" target="_blank">[Lua] -- only edit stuff below here ---------- local m_pets = "mypets" -- these
To set this up, make a new addon and create a toc file (google for the format or check other addons) for it and call it whatever you want so it's not easy to single out a group of people using the same named addon. The next thing to do is edit the four top variable at the top of the file, make sure these are the same for both people and DO NOT leave them as default - this is what the addon uses to communicate with the other person when to queue, when queue pops etc. The next few variable indicate how to communicate with the other person, via party whisper, addon channels etc. max_decline_count indicates how many times you should decline an invite if the queue doesnt pop for the other person to get them out of the queue, set this to 0 to keep declining. a_cmd is the slash command to start it. One person needs to type this command as well as a space something after it (the other only types the command and nothing else), they are the person who initiates the queuing This is the person who should have a level 1 and two level 25s as the other person then automatically equips pets to match.