Combine cranberries, sugar, orange juice and sauce water in a small saucepan. Simmer for 8 to 10 minutes, stirring, until berries burst and sauce thickens; remove from heat and cool for 3 minutes.
Heat the oven to 375°F. Warm turkey with broth in a covered skillet over low heat for 5 to 8 minutes until the meat reaches 165°F, then drain excess loose liquid.
Place baguette bottoms on a rimmed sheet, spread with cranberry sauce and layer on warm turkey and Brie. Set tops beside them cut-side up.
Bake for 5 to 7 minutes until Brie softens and bread is lightly crisp, removing plain tops early if they darken.
Add arugula over the warm filling, close with the tops and cut each sandwich in half before serving.