I have a chunk with 78218 cameras, 7372 of which are disabled and have no estimated positions. When I export all values (all checkboxes) from the GUI (12 decimals of precision) in tab-delimited format, all of the "enabled" flags are set to 1 regardless of whether the image is enabled or disabled.
-EDIT- when I calculate this flag as 1 or 0 based on whether the "estimated lat" value is present or absent, regardless of the value all images still import as enabled.