Once again, I was not absolutely clear.
Yes, there is a wye at Union station, or at least in the 1980's and I believe I saw it in Google maps about 3 years ago, it is how the Amtrak got into Union station.
I also thought the Illinois Central ran their commuter trains backwards in steam days, that's why the light way up on the tender of whatever engine that is at the Illinois Railway Museum, maybe #110??? 3709