Js gorden.
Hello & Welcome to the Forum.

I'm not sure if fasttrack has any different properties than other rail, but  a 2% grade is average, 4% can be considered.
Some locomotives will pull a larger grade ~ 4% - 9% depending upon, motor size, number of motors, traction tires,
number of cars being pulled.

example:
 an 0-4-0  pulling a tender & 3 cars would have no difficulty on a 2% grade, but would break traction & spin on a 9% grade
 a  2 truck shay pulling a string of logging cars should be able to manage a grade of 9% or more

Happy Rails.
Dave