While these cards have been unusable in Japan for the past 2 years or so, it looks like Mastercard has finally fixed the issue! The following notice was posted to their website recently:
To: Cardholders of Maestro-branded EMV Cards issued outside of the Asia/Pacific Region
All Maestro-branded EMV cards issued outside of the Asia/Pacific region are able to withdraw currency at Seven Bank and AEON Bank ATMs
There is a Seven Bank ATM located almost right opposite our Fukuoka school at the Seven Eleven, and just down the road from our Tokyo school at the Seven Bank branch on Yasukuni Doori.