Preheat oven to 325°F with rack in middle. Bring wine to a simmer in a small saucepan. Stir in porcini and remove from heat. Pat veal dry and season with 3/4 teaspoon salt and 1/2 teaspoon pepper. Heat 2 tablespoons oil in a wide 6-to 8-quart heavy pot over medium-high heat until it shimmers, then brown veal, turning, about 12 minutes. Transfer veal to a plate. Discard fat from pot and add remaining 2 tablespoons oil. Add pancetta and saute over medium-high heat until it begins to brown. Add onions and saute until softened, about 8 minutes. Drain porcini in a fine-mesh sieve set over a bowl, pressing on mushrooms and reserving wine. Coarsely chop porcini and add to pancetta mixture with carrots, celery, and garlic. Saute until softened, about 8 minutes. Stir in wine and cook until most has evaporated, about 2 minutes. Coarsely chop tomatoes and add to pot with their juice. Simmer, stirring occasionally, until thickened, about 15 minutes. Add veal with meat juices from plate, rosemary, bay leaves, and olives. Cover pot and braise veal in oven, turning roast occasionally, until center of meat is fork-tender, 2 3/4 to 3 hours. Transfer veal to a cutting board and let stand, loosely covered. Simmer sauce over medium heat, stirring occasionally, until thickened, about 10 minutes. Season with salt and a pinch of sugar if desired. Cut off strings from roast and discard bay leaves and rosemary. Thickly slice veal and return to pot, basting with sauce.