Besides copying of eb\data\world\maps\campaign\imperial_campaign to eb\data\world\maps\campaign\barbarian_invasion you need to copy eb\data\text\imperial_campaign_regions_and_settlement_names.txt to eb\data\text\barbarian_invasion_regions_and_settlement_names.txt
Also you will need to edit eb\data\world\maps\campaign\barbarian_invasion\descr_strat.txt to uncomment options bi line and edit EDU to allow shieldwall for some units.