It's not uncommon and nico video is a fairly popular platform for various kinds of live streaming in Japan. I'm not an expert on the topic, but I know a lot of artists stream themselves drawing pictures, and I know there are also a lot of camwhore-style broadcasts.
Also, they will use video cameras; they'll just generally go to lengths to make sure their faces aren't shown. Through wearing a mask or by very careful camera angles or such.
The author doesn't really go into a whole lot of detail about how the stream is specifically structured, though, so if you think about it too deeply you'll just be left wondering and things will seem a bit inconsistent.