At my local Subway, they said they supported it but they couldn't get it to work (and I could't even find their NFC reader-- it clearly wasn't connected).
At Subway it is built into the Verifone PIN pads they have, when they hit credit the contactless logo will appear and you can tap (like at Home Depot). If they hit mobile, as they've been trained (wrongly) to do in Missoula, MT, it will instead bring up a QR code for the Subway app (similar to MCX).