WP&Y is a hit-and-miss for steam if you go there. Most go by ship, of course, so you're at the mercy of the sailing time and what arrangements the cruise line has with the RR.
I've been there twice; once in 2000 (on my honeymoon, where my bride and I had our first big fight, over me wanting to take more train shots) and 2015 for an anniversary trip (no argument that time as she'd given up on changing me by then). On the first trip, 73 had left before we departed the ship, so a steam option wasn't available. I did get to see her coming back into Skagway later that afternoon so I got good shots and video (hence, the argument).
In 2015, we passed 73 sitting outside the shops and her smokebox lid was on the ground. I read they steamed up a few days later.
Unless you go there specifically for a scheduled trip, don't count on even
seeing steam, let alone riding it.
-Lee
Flickr photo set of my On30 layout