Lets start with a big disclaimer as what I am going to share is not exactly how things were intended… So If you are going to use any of this information do this at your own peril.
Normally if you go to you connected desktop –> BIM360 to a project and your files you will see that the explorer changes and you have very few functions. You can drag a file from here to your machine and you will get a copy. That works as intended.
But if you try to copy the file to another BIM360 project it does not respond. (at least for me) But when I started searching around on my harddisk I ran into this folder where I found some Revit files. (be aware these files are cloud models and not from Design Collaboration)
C:\ProgramData\Autodesk\CDX\WD\aec6ac8c-a512-497e-8009-f4aecbb7f1a5\SymLinks\BIM 360-workspace ( The Blurred out directories are all the Hubs I have access to) Notice that you see all the explorer functionality where in the connected desktop folder you do not see that.
If you look around in the folders you will not find files everywhere. See the difference below between the folder in the Desktop Connector and the folder as you find them in the ProgramData folder.
If you tell the Desktop connector to download a file it will also appear in the ProgramData folder. If you open another Hub and project in the ProgramData folder you can copy files between BIM360 companies / Projects. Because Connected desktop will see the new files appearing and it will start to upload them to the other project. I have tried a folder with files but I get the feeling that the Connected Desktop is not allowed to create new folders in BIM360 in this way. Which is odd as the interface allows it
So yes, through the Desktop Connector you can copy files between Hubs. Just be careful.