It hit me like a poisoned arrow that this popped not up on my quick searches...
When jumping on the postbox right to the left out the AH entrance and then jumping between the lantern and the wall behind it you get stuck between them.
one more jump straight towards the lantern and you're done, ideal spot to pose with your new rare mount^^
twocents just my two cents for I have not contributet for a while since walljump-fix in 2.4^^
EDIT: Screeny evidence just to feed the trolls :3