Cut the chicken tenderloins into 1-inch cubes. Toss chicken with 1 teaspoon salt, 1/2 teaspoon pepper, and Italian seasoning and coat evenly.
In a large skillet, heat vegetable oil over medium-high heat until it begins to shimmer. Add the chicken in a single layer and cook without stirring, until one side is browned about 2 minutes. Turn the chicken and brown the other side. Remove the chicken to a plate and set aside. Wipe out the skillet.
Cook pasta according to package directions. Drain pasta well.
Meanwhile, while the pasta is cooking, begin the sauce; Melt the butter in the skillet. Add onion, garlic, and mushroom and saute until veggies are soft, about 8-10 minutes. Stir in flour, 2 teaspoons salt and 1 teaspoon pepper and cook for 1 minute. Slowly add the milk and half and half and stir constantly, until smooth. Stir in Parmesan, Mozzarella, and cream cheese and cook gently until cheeses are melted. Add reserved cooked chicken and tomatoes. Serve over cooked pasta.