GTW on the way back will be cool too, but their map to Durand shows it passing along the lake and through KZoo ... so I expect Michigan Central.
http://www.sp4449.com/chicagoarea.png
An update on their website ...
"*UPDATED!* Chicago Union Station - We regret that we are unable to provide a public viewing of the steam locomotive in Chicago. The SP 4449 is too tall and wide to fit inside Chicago Union Station, and we have not been able to find a public area for it to be on display. In the past few days we also learned that a bridge south of Chicago is too narrow for the steam locomotive.
Due to the impassable bridge and in order to make it to Train Festival, on the evening of Saturday July 18th the 4449 will be taken off of the train just prior to its arrival at Union Station to be serviced, refueled and rehydrated. The Amtrak engine will spot the train at Union Station as planned. The 4449 will then move on its own (no train) to Congress Park to take a slower detour route on a different railroad to Michigan City. On the morning of July 19th, the train will depart from CUS at 8 AM, led by Amtrak over the planned route from Chicago to Michigan City to catch up with the SP 4449 for the remainder of the journey to Durand. Stay tuned to our 'tweets' for updates."
So it looks like Michigan City is a good place to find 4449 on Saturday evening / overnight into Sunday AM ...