Heat 2 tablesponns extra virgin olive oil in heavy large skillet over medium heat. Add sausages. Cover skillet and cook until sausages are brown and cooked through, about 8 minutes per side. Transfer sausages to plate; tent with foil to keep warm. Add garlic to drippings in same skillet and stir 30 seconds. Add broccoli rabe and 1/2 cup broth. Cover skillet and cook until broccoli rabe is crisp-tender, about 8 minutes.
Spoon polenta onto 4 plates. Top with sausages, Parmesan, broccoli rabe and drizzle with Prune Sauce.