Spray 13x9-inch (3-quart) glass baking dish with cooking spray. Cut bread into 24 (3/4-inch-thick) slices. Spread 12 slices with cream cheese and preserves. Top with remaining bread slices to make 12 sandwiches. Arrange in baking dish, pressing together if necessary to fit.
In medium bowl, beat eggs, milk, 2 tablespoons sugar and the salt until well blended. Pour over bread in dish. Let stand 5 minutes. Cover tightly with foil; refrigerate 8 hours or overnight.
Heat oven to 400°F. Uncover dish; drizzle with butter. Cover with foil; bake 10 minutes. Uncover dish; bake 15 to 20 minutes longer or until golden brown.
Meanwhile, in 2-quart saucepan, mix water, 2 tablespoons sugar and the cornstarch. Stir in 1 cup of the blueberries. Heat to boiling over medium-high heat, stirring constantly. Reduce heat to medium; simmer uncovered 1 to 2 minutes, stirring constantly, until slightly thickened. Remove from heat. Stir in remaining 2 cups blueberries.
Serve topping over French toast.