Thanks Marco. I might just go up there and check it out anyway. I've never been past the lake, only been up there when we do our work on Jenny Creek Trail. Are the trestles on the Winter Park (West) side or on the Rollinsville (East) side?
There are some really cool trails up there just past the tunnel itself, it is the headwater of Boulder Creek and we've done some hiking and exploring up there. Watching a train come out of the tunnel is really cool too, they've got these gigantic ventilation fans that are about as big and powerful as jet engines!