Place a rack in the upper third of the oven. Preheat oven to 350 degrees F. Cut tops off tomatoes; reserve. Hollow out tomatoes. (Reserve pulp and seeds from one tomato.)
For stuffing: In a large skillet heat canola oil over medium. Add sausage and chicken livers. Cook, stirring to break up sausage until no longer pink. Add onion, celery, sweet pepper, and garlic to skillet. Cook, stirring occasionally, until vegetables soften, about 5 minutes. Stir in rice, parsley, Worcestershire sauce, Creole seasoning, sage, and reserved tomato pulp and seeds. Season to taste with salt and black pepper. Remove from heat; let cool slightly.
Spoon stuffing evenly into each tomato. (Stuffing may overflow a bit.) Transfer to a shallow baking pan. Top each stuffed tomato with reserved tops. Generously drizzle with olive oil; season to taste with salt and black pepper. Bake 25 minutes or until tomatoes are softened.