Question: how 'public' is public, actually? Especially, how 'public' are 'public lectures'?
Many universities go out of their way to organize lectures that are accessible to anyone who's interested. This means, however, only that an institute choses to liberate only a small part of the information available, at a carefully picked place and time. Generally, the effect is that only visitors from a small circle will attend, not the general public. Most of the time, this isn't out of a lack of interest. It could be that the institute is, despite the open entrance, not easily accessible. Or that people outside the confined universe of the institute don't know when or where the public lecture is. Or think about the psychological barrier someone who's not accustomed to a university might have.
All in all, it's pretty safe to argue that, however good the intentions might be, public lectures are, in fact, not completely public.
The logical next question could be to think about how to increase the public character of those lectures. Think about the biblical public sermons, for instance. Jesus preached on the mount and on the plain, he went towards the public to share his view. If that idea is converted to our times, "Sermon on the Train" isn't that far-fetched.
Here, well known academics, as well as artists, go out into the public realm to share their ideas. Or, more precisely, they hold a lecture on a train in South-Africa. The lecture is announced beforehand by means of posters and such, meaning that people who want to hear the lecture mingle with the normal traveling public.
The difference is that the commuting public didn't choose to listen to the lecture, they are immersed into it, simply because they cannot get out of the train. In that essence, it's a bit like preaching in public - hence the term "sermon". One could ask whether this is more public as the traditional form, what the relation between lecturer and audience is, and who can access (or owns?) the information.
The idea behind the sermons stems from the artists "Made You Look". That means Nare Mokgotho and Molemo Moiloa.
"The works of Made You look are, as the name suggests, tongue-in-cheek interventions that encourage a re-observation of and de-familiarization with the ordinary." as they say themselves.