In a large skillet, warm oil over medium heat and saute bacon until browned and crisp; remove to a paper-towel lined dish and set aside.
Add onion, garlic, carrots and celery to fat remaining in skillet. Saute until onion is translucent and limp, 3-5 minutes. Transfer to a slow cooker using a slotted spoon. Discard any fat remaining in pan.
Pour tomatoes into a large bowl. Squeeze the tomatoes with your hand, crushing them into pulp. Pour pulp and juices into slow cooker.
Brown beef and sausage in skillet. Drain off excess fat and add to slow cooker, along with bacon, mushrooms, tomato sauce, tomato paste, wine, stock, basil, oregano, bay leaf, salt and pepper. Cook on low for 4 hours. Serve sauce over hot pasta. (Remove bay leaf before serving.).