The Trenton project and the development of the blueprints went through the appropriate kind of security requirements checklist. Those blueprints were deemed to be unclassified. Treasury Board, under the government security policy, now recognizes that there are no document-handling requirements for unclassified blueprints. The story is not much more complicated than that.
I would simply say the allegations that there were other copies of the blueprints remain, I believe, unfounded. Whoever found the original blueprints apparently argued that there were other tubes in the same place. It was not confirmed, as far as I know, that there actually were copies of the blueprints in those tubes.