In a large bowl, toss the chicken with 2 tablespoons olive oil and 3 tablespoons rosemary; season with salt and pepper. Cover and refrigerate for 30 minutes.
In a medium saucepan, combine the vinegar, 1 tablespoon olive oil, the onion, garlic, rosemary sprig and Worcestershire sauce. Add salt and hot pepper sauce to taste and bring to a boil. Reduce the heat and simmer for 2 minutes.
Preheat a grill to medium, add the chicken and cover the grill (or heat a grill pan over medium heat, add the chicken and cover loosely with foil). Cook the chicken, turning and brushing with sauce every 5 minutes, until golden and cooked through, about 40 minutes. Let rest.
Heat the remaining olive oil in a large skillet over medium-high heat. Add the tomatoes and the remaining rosemary. Cook, shaking the skillet, until the tomatoes blister, about 5 minutes; season with salt. Serve the tomatoes alongside the chicken.