Thanks for the clarification. I falsely assumed abandonware as public domain. I also found some explanation about the public domain here: http://programmers.stackexchange.com/a/72916
There's also the small problem that not all countries have a concept of a copyright in the first place. Quite a few EU nations have laws around the concept of Authors' Rights instead. Public domain does not even exist for those (because there is always an author, and authors always have rights to their work, even if they're publishing anonymously).
At least here in Portugal, while we do have Author's Rights (which include moral rights) instead of copyright, they still expire to Public Domain, and I believe the same is true for most EU nations: https://en.wikipedia.org/wiki/List_of_countries'_copyright_l...
Authors' Rights expire, but (at least in Germany and Austria) you cannot voluntarily put a work into public domain before and give up your rights on it, like you can under the US concept of Public Domain.
As far as I know all EU countries are signatories to the Berne convention on copyright, and so all of them have the concept of copyright. It is just that copyright is not the only intellectual property rights that apply, as you pointed out.
Authors rights (or "moral rights") are not a big problem. While you usually can't sign those rights away, they don't generally prevent the author from signing away distribution in perpetuity, so while you can't get "total" public domain in those cases, you can usually sign away most of the rights people are most interested in.