the security line discussion is a red herring
there should be no way to remove the background in the first place, if it was scanned from one image and printed ONTO security paper.
but if you did use Photoshop and remove the black ink from the green background then there would be no way for the program to know what was behind the ink- it would not automagically fill in the security paper lines.
What is Papit doing to give it different looking security lines? Using photoshop? Or could be that it is Dr. Conspiracy is tinkering with the image he was sent in order to make Papit look deceptive or not experienced?