Appropriately, the Maps code also alludes to sharing your mass transit trips with others, including the exact time you arrive at a given stop. There would also be shortcuts for favorite stations, potentially to influence Maps' directions.

It could be a while before you see these updates in an app you can use, assuming they show up at all. Hidden code like this can persist across multiple releases and might get cut if it's not ready or doesn't work as expected. However, the combination suggests that Google wants to do a lot more with location sharing than it has in the past -- it'd offer better insight into what you're actually doing.