In that era typically only things recorded in studios would be video, the rest would be film. So Connections could certainly he remastered, and I hope the BBC does so. Some of their older documentaries, like Ascent of Man, already got that treatment.
I think it was on film because it was released only a year later in the US. That was very difficult for shows on tape because of the 50Hz-vs-60Hz difference in video formats.