Comparing an underground rail system to a surface bus system is apples and oranges.
What lets the transit app do this is a that the MTA just enable Wi-Fi and cell signals in all underground stations after a long build-out so that the data can actually be collected system wide from riders using their app.
Sydney Australia has had this for several years, including through it's various tunnels. Whilst the majority of the network is above ground, the inner-city is underground. The telcos here spent a lot of money/time in getting 100% coverage through the tunnels in ~2011 though, which definitely enabled something like this.
Glad to hear that cell signal is finally reaching across the subway network - when I was last in NYC it drove me nuts not being able to just browse on my phone whilst waiting for a train.
Seattle has had a similar app, One Bus Away, for busses, for a long time: http://onebusaway.org.