I have used the following code to get the IBA internal names.
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ArrayList<String> result = new ArrayList<String>();
TypeIdentifier identifier = TypedUtility.getTypeIdentifier(typeDef);
TypeDefinitionReadView typeDefView = TypeDefinitionServiceHelper.service.getTypeDefView(identifier);
for (AttributeDefinitionReadView attDef : typeDefView.getAllAttributes()) {
AttributeDefDefaultView ibaRefView = attDef.getIBARefView();
if (ibaRefView != null) {
result.add(ibaRefView.getLogicalIdentifier());
}