Cook 2% milk over medium-high heat in a heavy saucepan to 180° or until tiny bubbles form around edge (do not boil). Remove from heat. Add tea bags and vanilla bean; let stand 15 minutes. Remove and discard tea bags, pressing liquid out of bags. Remove vanilla bean; scrape seeds from bean into milk mixture, and discard bean. Add evaporated milk, stirring with a whisk.

Combine sugar and next 9 ingredients in a medium bowl. Gradually add milk mixture to sugar mixture, stirring constantly with whisk. Return milk mixture to pan. Cook over medium heat until mixture thickens and coats the back of a wooden spoon, stirring constantly. Transfer mixture to a bowl. Place over an ice bath and cool completely, stirring occasionally.

Pour milk mixture into the freezer can of a 2- to 3-quart ice cream freezer, and freeze according to manufacturer's instructions. Spoon ice cream into a freezer-safe container. Cover and freeze 1 hour or until firm.