Hi John,
I don't recall Triple Crown running the Toledo-Cincinnati corridor. However, CSX briefly had the Xpressrailer service in the late 80's from Detroit-Atlanta using the Toledo-Cincinnati corridor enoute. Fort Wayne was the main hub for Triple Crown where the TC trains from other points would connect. The SB trains would then run from Fort Wayne-thru Cincinnati on to Atlanta and Jacksonville.
I honestly couldn't tell you what number of trailers would require a second engine, although, on one occasion, when I rode the Triple Crown train to Toronto, we picked up a second engine at Windsor.
Appreciate your interest.
Jon Stachowicz