The cactus are indeed still there, but in the 7 years since I first photographed them they hadn't grown much, if at all.
I find this all very curious. If I were going to plant opuntia on my roof I'd go a little wild. If one or two plants made it through the first year then maybe a dozen plants would follow—but that's me. Obviously these folks are happy with just the two plants. Good on them. I am happy to see they're still there all these years later.
Weather Diary, Jan 26: Hi 41, Low 35/ Precip .20—some of which fell as snow