Let me try to explain what I am asking a bit more precisely. Amtrak has a certain number of trains to run on each day and has to ensure it has the locomotives and the coaching stock in place to run these services. Therefore one has to assume that some form of planning is undertaken to make sure this is the case. In most European railways a certain depot has to allocate a certain amount of locomotives to the same amount of "diagrams" or "cycles". The locomotive then sets off on its daily which has been planned and barring any failures, late running and other operating incidents it can be assumed that this locomotive will stick to "diagram" until the end of the day where it will more than likely move on to another diagram. In Germany and Austria, these diagrams can involve 30-odd day plans where the loco wont will start on diagram 1 and finish up on diagram 31, 31 days later in theory.
There must be something similar planned by Amtrak, although obviously not that intensely due to the large distances Amtrak trains travel. But at the moment I'm mainly interested in the workings into and out of Chicago.
Any more questions feel free to ask
Thanks
Damian