Not quite a similar situation on my LAX-YVR flight the other day, but Y passengers continued to come forward to use the J washroom. [Both in the back were working.] I guess now that they must leave the curtain open on tansborder flights -- security bull**** -- it is open territory. Fortunately, there was no line up, just a steady flow of passengers from the back using the J washroom. I would have complained, but didn't want to appear too anal about it...