To prepare crust, lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and 1/4 teaspoon salt in a bowl; cut in butter and shortening with a pastry blender or 2 knives until mixture resembles coarse meal. Add vinegar and ice water, 1 tablespoon at a time; toss with a fork until moist. Gently press the mixture into a 4-inch circle on heavy-duty plastic wrap; cover dough with additional plastic wrap. Roll dough, still covered, into a 12-inch circle; chill 10 minutes.
Preheat oven to 425°.
Remove 1 sheet of plastic wrap; let dough stand 1 minute or until pliable. Fit the dough, plastic-wrap side up, into a 10-inch round removable-bottom tart pan. Remove plastic wrap. Press dough against bottom and sides of pan. Fold edges under. Line dough with a piece of foil; arrange pie weights on foil. Bake at 425° for 10 minutes or until edge is lightly browned. Remove pie weights and foil; cool on a wire rack.
To prepare filling, heat a large nonstick skillet over medium heat until hot. Add bacon, and cook 4 minutes. Remove bacon from pan, reserving 2 teaspoons drippings in pan; set bacon aside. Add leek to drippings in pan; cover and cook for 20 minutes, stirring occasionally. Sprinkle with 1/4 teaspoon salt and 1/8 teaspoon pepper. Remove from heat. Arrange leek mixture and bacon in prepared crust.
Combine egg substitute, milk, 1/4 teaspoon salt, and 1/8 teaspoon pepper; stir well with a whisk. Pour the milk mixture into crust. Bake at 425° for 25 minutes or until a knife inserted in the center comes out clean; let stand 10 minutes.
Note: You can use a commercial piecrust (such as Pillsbury) in place of the pastry crust. If you substitute an refrigerated piecrust, follow the package instructions for prebaking. It will add 15 calories and 1.4 grams of fat to the nutrition figures for each serving.