Sometimes, the MTA publishes “exclusive” details on subway and bus outages via their Service Status widget, which I’ve embedded below.
(1) Click on “Subway” or “Bus” in the horizontal menu bar
(2) Look for your Subway or Bus line in the vertical column. If it says there’s a problem, like “Service Change”, “Delays”, etc, you can click for more info.
You can also find this widget on mta.info.