Being on a NYC subway train is an even more interesting case, because depending on the precise client setup there's often intermittent or bad connectivity but rarely a good sustained connection between stations.

As in most of the world, smartphones are pervasive in both of these contexts.

Mobile and computer apps used to support these cases a lot better. As Bay Area connectivity has gotten better in those areas where well-off techies congregate (e.g. not underground Muni Metro), apps have gotten much worse at this except for apps targeting developing countries like India and Africa.