There are several hulks of old steam locomotives that used to operate on the White Pass still in Skagway. The White Pass currently has two locomotives that when in operable condition are used as steam power.
OF 2-8-0, #69 - known as the Gila Monster, would be a C-31 in Rio Grande parlance. She's a beast.
IF 2-8-2 #73 - a beautiful example of the locomotive builder's art at the end of modern steam. I would say she's comparable to a K-28.
These two locomotives handle what the White Pass wants it would appear. When my wife and I rode seven years ago the 69 was in the shops and the 73 was handled the steam up the hill.
The sheer volume of trains the White Pass operates, combined with the tight time frame as dictated by the cruise ship arrival and departure schedule would, in my mind, prohibit the use of more than one steam locomotive per day.
Breakdowns on the single track mainline could tie up hundreds of passengers for hours they can't afford to lose and make their cruise ship connection.
Having said that, if the White Pass wanted more steam power, the K-37's could certainly handle the physical plant and vice versa of the current White Pass operation.