Pastor, I hate to throw water on your sermon but there was no such thing as that for a literal train name or locomotive name.I am 65 years old born and reared in Chattanooga.I have hundreds of timetables for the region. Nobody has produced real railroad info about that being a literal name.
I have so many equiment lists, no serious railroad produced mention anywhere of a chattanoga choo choo. I have several books on the Southern RR and the Norfolk and Western, the ones which would have been inolved.
A reporter nicknamed the new train from Cinncinati to Chattanooga as the Chattanooga Choo Choo. Just a nickname that stuck.This was the early 1900's I think
The song was written in the 40's. I have never seen any proof that a specific train was meant.
Now for solid info, the route was Pennsylania RR from NYC to WAS. Southern RR from WAS to Monroe/Lynchburg. Norfolk and Western Lynchburg,Roanke, Bristol. At Bristol they changed back to the Southern RR which then took such trains through Knoxvile to Chattanooga. Beyond Chattanooga they went variously to Birmingam, to NOL and to Memphis.
The oldest train name was the Birmingham Special. The Tennessean name started in 1941(replacing the Memphis Special) and the Pelican name was taken in the late 40's.
Personally I have aways thought the Birminghm Special was meant. The song says it left NYC quarter to 4. Well, for years the BHM Special left WAS at that time so that seems close enough.
All were gone before Amtrak.
I saw the google reference. It says it was composed on the Bimingam Special but much further down says it does not refer to any one train.