Very interesting and seems a practical way to keep snow from ruining the shrubbery. I haven't seen this before in the Tokyo area, but then again snow is quite rare in Tokyo. Sometimes I wish I lived farther north; would be awesome to have a white Christmas!
I don't know how practical it is, but it works, and it protects a lot of beautiful trees. I really have no idea how common the practice is, but I've seen it in a few places.
Having snow is what makes winter bearable for me. Without snow it's just cold.