I received this message from Ken at
Blue Iris Support:
"The file is not compatible with 4. You can only import a version 3 settings file by double clicking it in windows ... like you did with version 3 days.Sorry for the misunderstanding there ..."
I take this to mean that the export setting sin BI3 will not import into BI4 and therefore one cannot migrate camera settings from BI3 to BI4.