This seems to fit the description of a 'database' given elsewhere in this thread, but it may be that some detail in the law allows things like this. Perhaps because it is a database that contains other things than art as well.
Certainly the database that google has backing its mapping service has commercial value in a much more obvious way compared to the wikimedia public artwork database.
I guess that the licensing agency either didn't know of this function, or else started with the easier target.
My baseless guess for the outcome if they sue google is that google would win on jurisdictional grounds after five years of battle.
§ 24 Works of art may be reproduced
1. if they are permanently located on or at a public place outdoors,
2. if the purpose is to advertise an exhibition and sale of works of art, but only to the extent necessary to promote the exhibition or sales, or
3. if they are part of a collection, in catalogs, but not in digital form.
As you may realise. There is a huge room for interpretation in the specificity, which is why we have courts & judges that settle these matters.
Sometimes I don't envy those engineers :p