Buses and trains already accept Mastercard, Visa and even American Express, which some UK transport operators don't accept. The days when NS only accepted Maestro and V-Pay are long gone.
I've indeed seen foreign passengers use a creditcard for paying their ticket on the bus and ticket machines in general accept them as well. But there payment happens via a regular payment terminal you'd also find in a store, so that's why it usually will work.
The real confirmation comes from
www.ovpay.nl which, after a bit of a search, mentions that foreign debit cards with Maestro or V-pay and foreign credit cards from Mastercard and Visa are accepted (as long as contactless payment is possible)
Maestro is in the process of being replaced by Mastercard across Europe, so shops like Albert Heijn will have to start accepting Mastercard, if they don't already.
Maestro is just a logo indicating it's a debit card with Mastercard technology, nothing more. Dutch banks already mention that abroad you'll be able to use your debit card anywhere where either Maestro or Mastercard is accepted. (V-pay debit cards are relatively uncommon)
But as the creditcard is not that common in the Netherlands, there are still stores which don't accept credit cards at all despite acceptance of debit cards with Mastercard (Maestro) or Visa (V-Pay) technology is universal.