These are excellent questions. Unfortunately finding any information on the Fort Wilderness RR is next to impossible. I can only guess at some of the answers.
The FWRR was Disney?s answer to a transport campers and guests through the campground, from the Outpost Depot (parking lot) to the Settlement Depot (Pioneer Hall). Disney forbids campers from driving their vehicles in the campground unless entering or leaving the campground. What better form of transportation in the wilderness is there than a steam engine?
The choice to use the small plantation type locos was most likely a result of Disney looking at Ward Kimball?s Chloe and Gerry Bests Olomana engines. These simple engines were used in Hawaii on tracks that were literally thrown down on the ground, and moved as needed.
Why Disney has Buena Vista construction lay the tracks was done mostly likely to save money (for the time being). They spiked the track right to the ties without tie plates and bent the track without a rail bender! One interesting note- I did talk to George Britton, and he told me in August 1976 he led a crew that re-ballasted & added tie plates to the entire line.
The fact that the FWRR turned out to be 3 1/2 miles long, and the engines had tiny boilers (holding 180 gallons, and a saddle tank that held only another 225 gallons) was a major over sight by MAPO. The solution to this problem could have been a additional water tower at the Settlement depot. The FWRR was built with one water tower at the Outpost Depot, and the saddle tank wasn't filled EVERY
time the engine stopped there, it was doomed.