If you look at that tree.js you'll see a function called _buildTreeNodeUrl. In that function you can see the repo tier web script call that gets invoked to return information about the node and the node's children.
The URL that gets built is something like:
If you look at the response that comes back you'll notice that the title is missing.
So in order to get this to work you'll probably have to extend that web script to add the title to the JSON that comes back. Once you do that, you can extend the Alfresco.DocListTree component with your own that retrieves the title that comes back from the web script.
This will likely be a fairly involved little customization and will require extensive testing to make sure that swapping that out does not have unintended side effects.