Here is what FVerbass and RedPhantom are talking about.

This UV mapping is done with Rizom UV Virtual Spaces (if I recall correctly, the Maya UV mapping is based on a subset of this software). In my humble opinion, it is the best UV mapping software available. I have a perpetual version and it is well worth the money. 

First, you "cut" the seams where you want the parts to be separated. The seams are represented with orange lines in the following image: The front and back are also cut at the shoulders. And the sleeves are also cut at the bottom so they will lay flat.

Then you "relax" the UV Map, using the Unfold button that is marked at the top of the image. You can then position the parts on the tile so that they all fit as shown.

I opened the shirt in UV Mapper Pro and used the Texture preview to show the result here: You will need to edit the CR2 to point to the OBJ with the new UV map in order to see the results.