Reducing cost can take a lot of tweaking to get right, and is likely to take more than one cycle to do. But new schedules do take some bedding in until they are running smoothly. Once that happens, you can then look for the next round of optimisations - tweaks to the way the trains are assembled in the yards which then start building the incremental gains.
If you have a better scheduling system, you build resilience into the schedule. You open up more time for maintenance, you keep your assets in better condition, so you have fewer breakdowns. One thing to remember is that (in general) there is a Pareto on train breakdowns - 20% of the locomotives cause 80% of the problems. It will be the worst locomotives that are taken out of service, so the reduction in service affecting failures should be quite significant.
You make some money on the OPEX side by doing more scheduled maintenance, and less emergency maintenance (overtime is really expensive!). You also make savings on the CAPEX side, because your assets last longer.
[edit]. Changed para order