Most of the WP&Y steam locomotives are in the lower 48. I know all of Dollywood's locomotives are former WP (some are former Army ones from WW2), Tweetsie has one as well. I think there was one running in the Midwest as well but it's location escapes me right now. I've gotten cab rides at Tweetsie and Dollywood on former WP&Y power.
For example, here's WP&Y 192 (a former Army locomotive) at the park's first version when it was called, "Rebel Railroad" in the 1960s:
As for the current RR, I've never seen 69 in steam but I have seen 73 twice. My wife and I took a cruise to Skagway in May of last year and of course that day was all about the trains (which drove her almost as batty as it did on our honeymoon to the same place, exactly 15 years previously to the day)... Sadly, 73 wasn't running that day.
Just an FYI, the easiest way to model a WP&Y steam locomotive in O would be to get a Bachmann On30 ten-wheeler and letter it to represent either #s 10 or 14, which both came to the line in 1943 from the East Tennessee & Western North Carolina RR. Both ran in ET&WNC green/gold paint and the road names painted over their first season there. Bachmann even makes # 14 in the green paint, so all you'd have to do for a WW2 version would be to paint out the road names and weather it down really well! They were sent to the NP shops in Tacoma for a complete rebuild after the first winter, the cabs were pulled back and plows added to the fronts. Both burned in a roundhouse fire at Whitehorse before the end of the war, though. They were shipped back to Seattle then scrapped at the NP yard at Auburn, WA after WW2 was over.
More info on WP&Y locomotives can be found by clicking here .