Why not Go South?

http://www.hansenwheel.com/

When the Canyon Diablo train robbers were captured on or about April 1, 1889, the posse and outlaws were probably closer to Flagstaff than they were to the Milford, Utah, railhead.

So, why didn't Buckey and his men just head back to Lee's Ferry and then go through the Painted Desert back to Flagstaff?  The main reason is that Buckey didn't trust his odds of four-on-four.  If the lawmen let down their guard, even for a minute, one or more of the robbers could get the jump on them with possible disastrous results.

So, the decision was made to bring the robbers back through Cannonville and on to Panguitch where a skilled blacksmith fabricated leg irons for each of the captives.  Two of the men were chained to each other.  Each of the other two men had irons on each leg and a chain between the irons.

You can read a Deseret News item describing the leg irons and chains here:
https://canyondiablo.blogspot.com/2020/01/robbers-descriptions.html

At this point there was no thought to trying to take the captives back south.  They obviously couldn't ride a horse and the route between Panguitch and Flagstaff was long and difficult for a horse drawn wagon.

Instead, the chained-up train robbers were put into a farm wagon and carried to the railhead at Milford, Utah.  A standard size farm wagon box back then was 38 inches wide and ten feet, six inches long, easily adequate to carry four men sitting on the rough boards of the bottom of the box.

There is no record of how the wagon was obtained or how many horses pulled it or who drove it....or even what it might have cost Buckey to "rent" it.

There is likewise no record of when the posse and the captives were actually in Pangutch.  The capture is said to have taken place on or about April 1 and the entourage arrived in Salt Lake City on April 10.  That's about the correct number of days to travel from the capture site to Milford and take the train north.

Even though the captives were kept in irons and chains, one of them did manage to escape at Raton Pass, New Mexico.

http://www.hansenwheel.com/