Basically, with this macro, you'll be able to leave a BG without the deserter debuff.
The macro:
/script AcceptBattlefieldPort(1, 1)
/script AcceptBattlefieldPort(1, 0)
You MUST enter the BG with the macro, or it won't work. So when the BG pops hit the macro, hit the macro again to leave the BG. Please note, it's kind of buggy and doesn't always work, I've found it works better when queing for one BG.
It also doesn't count you as a slot in the BG, while this means you won't be able to see the score board, you're team will have an extra team member. However, the player cap still exists within "X" BG. Meaning, if you join an AB. (In my case, I'm horde), then horde will have 16 people, and alliance with have 14 (assuming noone else is using this, obviously)
As I said though, I don't foresee this being around forever, so enjoy it while you can.
Happy sploiting