Just used it in a local Kangaroo Mart at a BP gas station here in Central FL. Mind you, this business is not on the "Apple Pay List" either.
Went to the terminal, had my phone unlocked, put the top of my phone to where you would normally put any other contactless credit card, and bam.. passbook opened with my Chase debit card and I put one of my TouchID fingers on it until it said transaction complete. Still had to hit "Yes" for the total on the pin pad, but then my receipt started printing. Worked flawlessly and even had some people in line asking me how I just paid with my phone, lol.
TL;DR - Works with other "contactless payment" terminals, not just merchants deemed good for Apple Pay. It says it right on their site. Just look for this: