Those are really two different questions, Greg.
The season pass program is pretty simple - buy one and you can get a ticket FOR YOURSELF any time you want. (You can't get tickets for others with it.) There are also upgrade provisions so that if you buy a coach pass you can ride in the Parlour Car or on the Moonlight Train for a nominal fee. (These fees are listed on the back of the pass.) Passes don't allow you to just step onto the train; they are more like a "credit card" that can be used to "pay" for tickets during the season.
As for getting on and off the train, there is no formal procedure for getting on or off at Sublette. Osier would be easy, of course. We have talked about creating and promoting a formal program, but there have been more urgent issues to work on.
If you wanted to use Osier as a starting point for a few days in the National Forests, simply book a ticket using your pass on the day you start, and another on the day you plan to return to civilization.
Just be aware that we will put you in the rider gon on your return trip
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