It depends on the line. Numbered ones have more accurate data, for example, as they rely on rail sensors to track trains. MTA recently pushed new Bluetooth-base

It depends on the line. Numbered ones have more accurate data, for example, as they rely on rail sensors to track trains. MTA recently pushed new Bluetooth-based technology to get location estimates on all the other lines. They're just estimates, still. It's really an MTA problem, though. You can tell because they now have screens with arrival times everywhere. Even if the screen says that a E train is coming in 11 minutes, one moment later the same train (another E train?) is just two minutes away, if not approaching the platform. Perhaps they only need to recalibrate the code that comes up with the estimates, since the beacon system is fairly recent.