Coat inside of Crockpot slow cooker with nonstick cooking spray. Add beans and tomatoes with chilies. Combine chili powder, cumin, and 1 teaspoon oil in small bowl; rub onto chicken.
Place chicken in Crockpot slow cooker. Cover; cook on HIGH 1 ¾ hours.
Transfer chicken to cutting board; slice. Transfer bean mixture to large bowl using slotted spoon. Stir in remaining oil.
To serve, warm taco shells according to package directions. Fill with equal amounts of bean mixture and chicken.