storage limits for shared files

I have an unlimited enterprise account (via my university in NYC). I collaborate with scientists overseas who have free accounts.

I would like to use box receive large numbers of files (terabytes of sensor data).  I would like to ensure that the overseas collaborators continue to have download/edit access to the files after upload.  

What's the best way to accomplish this?  

More generally, my understanding is that items that a given user owns in Box will count against that user's storage.  But what governs who owns a file uploaded to a shared folder? Does ownership stay with the uploader? Does it flow from the ownership of the receiving folder?