Combine first 3 ingredients in a medium saucepan; bring to a boil. Add cornmeal in a slow, steady stream, stirring constantly. Reduce heat to medium, and cook, stirring constantly, 20 minutes or until cornmeal mixture (polenta) pulls away from sides of pan.
Trim fat from tenderloin; cut tenderloin into 3/4-inch pieces. Coat a nonstick skillet with cooking spray; add oil. Place over medium-high heat until hot. Add meat, pepper, and garlic; cook 4 minutes or until meat is browned on all sides, stirring often. Remove from skillet. Drain and pat dry. Wipe drippings from skillet.
Coat skillet with cooking spray; place over medium-high heat until hot. Add mushrooms and shallots; saute 2 minutes. Add wine and tomatoes; bring to a boil. Reduce heat; simmer, uncovered, 5 minutes. Stir in tomato paste and thyme; simmer 3 minutes, stirring occasionally. Return meat mixture to skillet, and cook until thoroughly heated. To serve, spoon meat mixture over polenta.