To prepare syrup, combine the first 4 ingredients in a medium saucepan over medium-high heat; bring to a boil. Cook for 10 minutes or until slightly syrupy. Cover and set aside.
To prepare fruit, brush outsides of apricots, peaches, nectarines, and plums with oil, and sprinkle cut sides of fruit evenly with 1 tablespoon sugar and cinnamon. Place fruit on a grill rack coated with cooking spray. Grill 4 minutes on each side or until tender. Place fruit on a cutting board; cool 5 minutes. Cut each fruit half into 4 slices.
Place 1/2 cup of ice cream into each of 8 bowls. Top each serving with 8 pieces of fruit and 3 tablespoons syrup. Serve immediately.