I definitely used an ATM at BCN last year, so there is one, but I'm pretty sure it's outside of customs.

Similarly, last year at CDG as a transfer passenger, I was forced to exchange money in order to buy water to take my medicine (caught a horrible cold) during a labour-imposed flight delay because there are no ATMs on the transfer passenger side. After the exchange spread and fee, my $20 bought me 0.5L water, a turkey sandwich, and a pack of breath mints. Uggh!