Facebook – How to export or share Google+ photos with Facebook

No. This isn't allowed per section 3 clause 2 of Facebook's Terms of Service:

You will not collect users' content or information, or otherwise access Facebook, using automated means (such as harvesting bots, robots, spiders, or scrapers) without our permission

The popular album downloader PhotoJacker was abandoned because of that. (Disclosure: The former developer is my friend.)

Apparently, sometime within the last three years, Facebook either fixed a bug or added a feature that makes this work (again?), at least for the post that this question was originally about.

Unfortunately, there are still some posts for which the menu doesn't even appear, however, when it does appear, it also does work, unlike three years ago, when I wrote this question.

So, I consider this a bug which existed back then, and has been fixed in the meantime, and thus I consider this question answered.