I did get to 1930s in the American scenarios, even I play the game until 1990s, I did not see the Challenger. For the European scenario, the latest starting year for the Europe map is 1870s. Since the game design limit the players running a railroad for 100 year only, I reach endgame in 1970 and can never play till 1972. Also, RE Class 6/6 never appeared before 1970.
I found two locomotives, the 4-6-6-4 Challenger & the Re Class 6/6 introduced in the game manual were not available in game. Any one know if there are special conditions to unlock the engines, or actually it's not included in game?