Combine oil and garlic in a cup and set aside. Pat shrimp dry with a paper towel.
In a nonstick skillet, warm 2 Tbsp. oil and 1 clove garlic over medium heat. Add shrimp and white portion of scallions and cook, stirring, until shrimp are opaque, about 3 minutes. Add beans, season with salt and pepper and cook, stirring, until heated through, about 2 minutes. Remove from heat and stir in tomatoes.
Preheat oven to 375°F. Arrange bread on a baking sheet and toast until crisp, about 8 minutes. Brush with remaining garlic oil. Stir scallion greens into bean mixture and then serve with toasts.
