On a not completely unrelated note, cloneObject() is cloning the object just fine (I can add the new one without getting the "already added" message), but when I try to translate it, it doesn't move. The docs say both objects would share the same mesh data, but I don't think that would be a problem. The following code is printing non-zero values for x and y, but isn't moving the cloned plane:
SimpleVector buildingCenter = currentlyBuilding.unitPlane.getTransformedCenter();
SimpleVector center3d = workerStandsWalksDies.getTransformedCenter();
SimpleVector destination = new SimpleVector(center3d.x-buildingCenter.x, center3d.y-buildingCenter.y, 0);
currentlyBuilding.unitPlane.build();
System.out.println("Translated? "+destination);
currentlyBuilding.unitPlane.translate(destination);