So...using Google Earth street view, where the old tracks cross the roads, it looks like the tracks are picked up until Paris, where the abandoned tracks are still in place.
I'd be interested to know how deep the gravel is along the unimproved sections.
I have ridden one of these rails/trails things in East Texas and it was very rideable on a mountain bike or even a hybrid.
In Celeste for example, it's paved:
http://maps.google.com/?ie=UTF8&ll=3...34840231720717
But then outside of town it goes down to doubletrack:
http://maps.google.com/?ie=UTF8&ll=3...23329437424983
Wolfe City:
http://maps.google.com/?ie=UTF8&ll=3...59756633253012
Ladonia:
http://maps.google.com/?ie=UTF8&ll=3...62782543447643
Etc. Etc. Etc.
I was wondering if there might be bridges or trestles out along the way.
The link mentioned the total distance would be 56 miles one way when completed?