If [1], of which I've only skimmed the summary, shows that the EC was aiming to "calculate a level of interchange fee that makes the merchants, on average, indifferent between a transaction by cash or by card", and if that's the level that's been implemented in the EU, then they can probably call it a success.
In the last 3-4 years, I've been surprised a few times when small businesses (plumber, street food seller, dry cleaner) have preferred a card.
