In those pictures what you see in Maya is actually the equivalent of a Sandbox 3 layer. This means you can now use your assets to build an actual Sandbox layer directly within your Maya scene (brushes, vegetation, etc...).
Then simply click "Export Layer to Sandbox" and after you've imported the layer in Sandbox you get exactly what you had in Maya!
And I just got it to work both ways! Meaning you can tweak your level in Sandbox, export the layer and update your Maya scene with just a click.