Plex is a separate company not connected with TiVo or Rovi. While there are a couple (or a few) other programs that can decrypt .tivo files, IIRC, all of them exclusively deal with TiVo files. Plex is a general purpose, multi platform media library system and the TiVo client is just one of several that they publish. I'm sure that Plex has an idea of how many people have actually used the Plex for TiVo client and considering it would be subset of TiVo users, I'm going to guess it's a smaller number than say the Roku client, the Apple TV client, the Fire TV client, the Playstation client, the Xbox client, the Android client, and the iOS client. It's probably not worth their effort to write a decrypt plug in for TiVo files (or at least not enough reward for spend the resources to do so). Incidentally, who's pushing this line that Plex is the official replacement for TiVo Desktop (and transferring files off of TiVos)? I don't recall seeing anything from TiVo on it.