I arrived under the same circumstances several months ago. Although the counters do not open, there is a little kiosk that does open earlier than 8pm. Unfortunately, it does not open until at least 4pm (if I remember correctly.) Also, they do not prioritize first or business class in this line. I therefore had to wait over an hour before I got to the front of the line. Another thing to mention is the incompetence of the staff manning this booth. Perhaps you'll get lucky, but during our experience, it took them an hour to check in three parties ahead of us. There is no way to access the lounge without a boarding pass, but once you get there...its one of the best lounges around.