I went to the box office last week (there were no rush tickets that day) and asked the agent. He said that if they have more then about 10 tickets, they usually open rush, otherwise they do not. I imagine this is not a hard and fast rule, but given that most days are selling out or only have a few tickets left, I say we are out of luck.
I wish I had seen it
Oh well.
That being said, if you're in the area, it doesn't hurt to try, right?