There was talk earlier this year that Ventura County (that owns the tracks) would terminate the lease with the railroad December 1. The county has been subsidizing the train at $600,000 per year, and they want to see the railroad's books, which the railroad doesn't want to open wide enough. I haven't seen anything recently about how that is going. My point: take it now.
There is an interesting little historical museum on the grounds. It baffles me that the museum is only open weekdays while the train operates weekends. There are also some parked rail cars used as a gift shop.
I spent some time in Santa Paula recently. The oil museum and ag museum were both well worth admission and there is lots more I didn't get to yet.
As to the tunnel, as FrensicPic said, anything to Loose Caboose is safe. Many of the themed trains go through the tunnel then park in the fruit trees, so you'll want to ask before taking a murder mystery that doesn't give particulars.
