Cook all beans in large pot of boiling salted water until crisp-tender, about 5 minutes. Drain; rinse with cold water and drain well. (Can be prepared 1 day ahead. Pat dry, then wrap in paper towels. Enclose in plastic bag and refrigerate.)
Combine beans, tomatoes, onion and basil in serving bowl. Whisk oil, vinegar and sugar in small bowl to blend. Season dressing with salt and pepper. Add dressing to vegetables; toss to coat. Cover; chill at least 1 hour and up to 4 hours, tossing occasionally. Serve salad cold or at room temperature.
