i wonder what type of tire they put on it?
the compound plays a huge part on how the tire performs.
If its too soft it can do exactly what you describe.
Too much drag caused by a soft tire can make it heat up, especially if you make long runs or are carrying heavy loads for long distances.
I would check the factory specs on the truck on the tires and see if the right tire was put on the truck.
I've ran across this alot in the past when customers buy a cheaper tire trying to save money and wind up with problems like this.
In the end its just not worth the headache to try and save money when getting the correct tire would save alot of trouble.

Of course it could just be a bad tire.
if the brakes are not dragging then it has to be a tire issue.

Make them replace it if possible, they are not supposed to separate, it would have to be getting extremely hot to cause this that quickly. Now if the wrong tire was put on because of a decision made by your company then of course they would not want to cover it.