Drupal Ubercart to Commerce Migration: any solution for uc_file (file downloads)?
Well as it turns out, no code was needed.

In case anyone runs into this issue, here's what you need to do:


Download the dev version of commerce_migrate_ubercart and apply the payment patch if it hasn't already been applied. 
Disable all Ubercart modules
Carefully follow the instructions in the README.txt file. You'll
want to migrate every available table starting with products, and
working your way to payments (transactions). Save the database early
and often along the way.
Download/configure commerce_file and commerce_license. 
Be sure you are able to go end-to-end with your cart and download privileged files in your user/uid/my_files tab. 
Download/enable commerce_vbo_views and views_bulk_operations
Edit the rule "Activates licenses of an order", and add the event "After updating an existing commerce order".
Go to your Store's order list page, select the desired order states
that have completed orders, then select all rows in the table, then
click modify order values, and just set the exact same state as
selected before. What we're after here is to force a re-save of the
order to trigger our rule.
You should now be able to view a user and click the "Files" tab to see their downloads assuming permissions are correctly set and the migration worked. 
Edit the rule again to remove the added event and you're done.


Easy peasy :)