It seems to be somewhat compatible.
I work in the card-payments space, but in the US. We can handle Maestro cards, so long as all parties are aligned to accept them. You need a shopping cart that doesn't scream "This card number looks weird" before even letting the customer submit it, a gateway that identifies it correctly, and a processor that's built to handle it. Probably the merchant account needs to be configured to accept it too, but that's outside my scope.
If the processor mentions Maestro at all, it's usually a corner-case line item in the documentation-- "Send field 923 = AA for Mastercard, and AB for Maestro, but everything else the same."
It's an interesting evolutionary divergence. We had/have "debit only" networks in the US (i. e. Star, Cirrus, Plus). They still exist but they are largely irrelevant for purchases because virtually every checking account provides a Visa or Mastercard badged card. There are a few situations where merchants can try to reroute the transaction to a debit network for lower fees, but it's a narrow interest at best.
They actually went through a legal tussle here because some merchants felt imposed on when the card networks said "If you take Credit Visa/Mastercard, you also have to take Debit Visa/Mastercard" back when the fees for doing so were higher.