To be exact, it was with a Sony A330. Ancient by today's standards and only 10.2 MP.
Here's a bit of trivia about the Sony Alpha series. Sony bought Minolta when Sony was getting into the SLR digital camera business. As a result, the Sony Alpha series used the "Alpha mount" for the lenses, which was essentially the same lens mount as used by the Minolta cameras. This resulted in the Sony Alpha cameras being compatible with a lot of the Minolta lenses (though not with the old Minolta MD lenses). Because Minolta was one of the leading camera manufacturers back in the 80s and 90s, there were a ton of good quality Minolta lenses in the market. So, in the same way the Canon and Nikon cameras were compatible with their respective film camera lenses, Sony also had a ton of film camera lenses they were compatible with. In practical terms, that meant you could get a lot of used lenses for cheap. (I have quite a few lenses and almost all of them cost me less than $100 each, some significantly less.) (I owned a Minolta film camera with a few good lenses so that's why I went with Sony instead of Canon or Nikon.)
I believe all the photos in the contest were taken with digital cameras, though I'm not 100% sure. I'd guess it's probably something like 98-99% are digital. I'm not sure how many are phone cameras vs dedicated cameras, though. With today's phone camera technology, they're essentially replacing the entry level cameras. (I think Olympus is abandoning the entry level SLR/mirrorless camera product lines for that reason.)
Hope this wall of text wasn't too boring for you.