I searched and didn't find this particular exploit as a alliance Paladin.
So first of all you need to be a paladin (and alliance)
So get as close as you can to the front of the entrance to the Sunreaver's Sanctuary as you can without getting teleported out.
Have crusader aura on it helps you get there in time.
Now use Divine Shield and mount up quickly. Now head towards the stairs straight ahead. Once you get to the top of the stairs take a left. Now go until you get inside and you see the catapult. Now go behind the catapul and to the right into the corner. Now once the sheild wears off get ontop of the catapult. Once you are ontop of the catapul, you can either chill up there, or go into the horde PVP room.
Now to get into the PVP room you have to wait till either your Forbarence wears off and you can use your Divine sheild, or when it wears off you use Hand of Protection to get in there. So for this part you want to get onto the top of the catapult and then activate Hand of Protection and then go into the pvp room (to the left of the catapult) now go to the back of the room and behind the portal and the chair sort of thing and go into the corner on the right. And now you are in the Horde PVP room!
If you have any trouble follow the screenshots!