natTable.addConfiguration(new DefaultTreeLayerConfiguration(treeLayer.getModel()));

	public void configureUiBindings(UiBindingRegistry uiBindingRegistry) {
		uiBindingRegistry.registerFirstDoubleClickBinding(
				MouseEventMatcher.bodyLeftClick(SWT.NONE), 
				new TreeExpandCollapseAction()
		);
		
		uiBindingRegistry.registerFirstSingleClickBinding(
				new CellPainterMouseEventMatcher(GridRegion.BODY, MouseEventMatcher.LEFT_BUTTON, treeImagePainter),
				new TreeExpandCollapseAction()
		);
	}

natTable.addConfiguration( new DefaultTreeLayerConfiguration( grid.getTreeRowModel() ) );

public class TreeGridLayer extends SortableGridLayer {

  // new variable
  protected ITreeRowModel<PersonWithAddress> treeRowModel;

  @Override
  protected BodyLayerStack createBodyLayerStack( List<PersonWithAddress> values ) {

    ...

    treeRowModel = new GlazedListTreeRowModel<PersonWithAddress>( treeData );
    BodyLayerStack bodyLayerStack = new BodyLayerStack( glazedListsEventLayer, treeRowModel );
    ...
  }

  public ITreeRowModel<PersonWithAddress> getTreeRowModel() {
    return treeRowModel;
  }
}