Bring 1 1/4 cups water to boil in heavy large saucepan; add tea bags. Remove from heat. Cover and let steep 15 minutes. Discard tea bags.
Add rhubarb, sugar and ginger to tea in saucepan. Stir over medium-high heat until mixture boils. Reduce heat to medium-low and simmer until rhubarb is just tender, stirring occasionally, about 10 minutes. Transfer rhubarb mixture to medium bowl. Refrigerate until well chilled, about 3 hours. (Can be prepared 2 days ahead. Cover and keep chilled.) Serve with Mascarpone Cream.
