There are so many ways that IT could improve existing public transportation. When I was in the Boston area I wished for a service that would text me in the morning and say the next inbound trains are M,N,P minutes away. Depending on N I could stroll to the station or hustle to make it on time.
Even when I'm in a top-20 city (instead of a top-5), I could still be persuaded to take the bus if IT systems make it easy and convenient.
Believe it or not, there are people working for these systems who are both willing and capable of making that happen. Unfortunately, there's a trump card of paranoid ass-covering which routinely squashes such aspirations:
Terrorism
I worked with a transit agency was not just capable of sending texts, but had a surprisingly slick mobile-ready, web app for displaying realtime, animated schedules in 2008.
Someone got up in a meeting and said 'What if terrorists use that information?'
Today, six years later they don't have so much as a reliable API available to the public.
The MBTA does this these days although its main use is w/ the busses, where it has been a godsend. Since the bus tracking apps arrived busses went from something I actively avoided taking to using all the time to navigate the spokes in the system for exactly the reason you state. I can watch from my computer or phone until just before a bus is coming in and hurry on out to the stop.
Even when I'm in a top-20 city (instead of a top-5), I could still be persuaded to take the bus if IT systems make it easy and convenient.