Hi Darryn,

The main reason behind adding the major bundles files to our atlas is that many studies investigate the diffusion characteristics of these bundles. One can download the major bundles files and use them as ROIs in an ROI-based analysis. The CC fibers would constitute a massive ROI and would cover most of white matter. Such an ROI would not be that interesting for ROI-based studies. That's why we left it out. But you can easily generate this and any other group of fibers you are interested in. Just read the "How to do HARDI tractography on the IIT Human Brain Atlas using MRtrix" http://www.nitrc.org/docman/view.php/432... 
 
Please let me know if you have any other questions.

Regards,
Konstantinos