The use of "excuse" was referencing the fact that these trains didn't just up from no where, that training on new trains isn't an unexpected thing for a train c

The use of "excuse" was referencing the fact that these trains didn't just up from no where, that training on new trains isn't an unexpected thing for a train company to need to do. It's like saying a product in a supermarket is delayed "because it needs to be put on the shelf"