Lightly spray a large saucepan with oil. Heat over medium-high heat until hot. Add lamb shanks and cook, turning, for 5 minutes or until browned. Transfer to a plate. Reduce heat to medium. Add onion, carrot and celery. Cook, stirring, for 2 to 3 minutes or until soft. Add garlic and cook for 1 minute.
Increase heat to medium-high. Return lamb to pan. Add tomatoes, stock and 2 cups cold water. Bring to the boil. Reduce heat to low. Cover. Cook for 1 hour 30 minutes or until lamb is tender. Remove lamb shanks to a board. Shred meat
Return soup to the boil over high heat. Stir in pasta. Cover and cook for 7 to 8 minutes or until pasta is tender. Add shredded lamb and basil. Season with salt and pepper. Ladle soup into shallow bowls. Serve with crusty bread rolls.