Yes, I believe the only requirement is that the cost can't exceed of a national transfer, which is unfortunately still not free everywhere in the EU.

I think you can also be charged if a currency conversion is involved (both directly and indirectly through poor exchange rates).

Euro denominated transactions within the SEPA zone (more than just the EU!) cannot be more expensive than domestic euro transactions. See https://nl.wikipedia.org/wiki/Single_Euro_Payments_Area .

But if your country doesn't use the Euro (i.e. the UK), domestic Euro transactions can be more expensive than domestic transactions in the home currency.

The same loophole is used in Bulgaria. Our largest bank charges 7 EUR for receiving 1 EUR, and 19 EUR for sending 1 EUR.