I was there the last week of May, and again in the early fall. Both times the tunnel was shut off. There was evidence that someone cut a man-sized hole in the blockade, and then it was re-sealed.
And that someone may have been someone at the jam (no, not me).
Throughout the summer, there were news stories about the DCNR trying to get funding to restore the tunnel, but they all stated that it would not be done last summer. I also have friends who were there in June and it was CLOSED.
I think you must be thinking of a different tunnel. We're talking about the one at Poe Paddy. Where you park at the Lykens Valley camp, cross the walking bridge, and the tunnel is ahead. It is part of the mid-state trail.