In theory there is no difference between theory and practice...
As for software, the optimization of rail slot allocation is far beyond spreadhseets - for the whole French network it is a math-heavy process for which a whole team harnesses a bunch of specialist software. More about the process (in French): https://tel.archives-ouvertes.fr/tel-01423840/document
Part of the problem in modeling is to also model the tens of thousands of humans interacting with the new schedule. Changing the train schedule also changes their schedules.
Hence, each time a schedule changes there is an uptick of accidents, disruptions, missed trains, overcrowding, etc until all adjust to this new timetable.
Cant u sort of simulate the expected scenarios and get sort-of expected performance?
I realize there is unexpected events, but these will occur anyway in old and new schedules
Also - does real train software has nice graphics or do u get a boring excel ? ;(