Then call them!

Tom,
I suggest you go right to the railroad and talk to Kim, Earl, or Dan and give them your proposal.
One of several things will happen most likely,
(a)They will tell okay but you have to....
(b)Our policy is we will for a Big Dollar figure!
(c) No way in Hell(except more polite)!
So rather than banter back and forth on the net, go to them with a serious proposal once and for all, and show them you are willing to back-up your intentions. They'll want a signed contract(if they approve it), and some other things.
For what it is worth on Craft's trips in 1992 we never ran mid-train helpers through the gorge from Sublette to Osier...We ran mid-train on both sides of it and doubleheaders in the middle for safety reasons. Remember this railroad is a bit fragile, and night running isn't high on the priorities in their minds right now. But I suggest you ask to find out the score!
I speak from a little experience here. Charters are fun, but not a lot of fun to be in charge of!
Everyone wants to do them, but few want to run them! There are risks for your rewards!
Happy planning!
Sincerely,
Greg Scholl