I was one of the first to stay in them when they opened them up Saturday of Memorial Day weekend. I had a water/elec site reserved and stayed at it Friday night and when I took a walk around the campground Saturday morning I saw all the full hookups and they were completely empty. I went down to the camp store and asked about them and they said "yeah we decided to open them up this weekend to see if anyone would be interested".... I immediately jumped ship to a full hookup site and when others saw what I had done the entire loop filled in about an hour.
With that said yes, they will hold some big rigs... Not all of them, but a lot will hold 40'+. Also be prepared that the sewer hookup is below ground in this vault thing and I couldn't get a real good connection with my elbow. I'm positive others have ran into the same problem. At least on the site I was on the connection was too far below ground level. Not sure if they are all like that.