Just the presentation layer
Twitter is just a presentation channel. And its 'news' because its free to send and free to receive. Taking the more public example of the RedFunnel ferries instrumentation: Twittering it (sorry, OK 'tweeting' , arghhhh) effectively disintermediates the SMS services which would otherwise be happily charging you 50p for a service update message. Yes you could do the same by updating statuses on a web page, or fetching them from a webservice, but you may as well tap into a bigger general infrastructure rather than run that part yourself.
AFAIK not inviting/expecting others to subscribe, apart from those interested in the end-to-end solution - its definately not a "listen to the minutiae of my life" situation like most Twits. Focussing on the surfacing of the events to today's fad (Twitter) is just the media's obsession. Instead the real IT story is about instrumentation - more sensors than actuators but the latter will rise when you subscribe to a twitter channel in the other direction.
Most disappointing is the fact he doesn't have a dog called Gromit.