Copy the file to "My Games/Beyond the Sword/saves/World Builder" and start a custom scenario with the file. Tested with plain BtS 3.19 or BtS 3.19 + BAT Mod 4.1.
For more infos, discussion or feedback see https://forums.civfanatics.com/threads/italy-128x144x18.663923/
For more infos, discussion or feedback see https://forums.civfanatics.com/threads/italy-128x144x18.663923/