Daniel, the Google Maps Community Manager, posted in the Google Maps Help thread that they've updated Google Maps/Transit to include a data feed from the MTA where they can post alerts of planned outages for NYC subways directly on Google Maps.
Here is a picture:
Daniel explained that Google Maps for Android or desktop, you will now see whether "any planned service changes are expected to affect that station at the time." "In addition, the relevant alerts will be included in the step-by-step transit directions pointing you wherever you’re going," he added.
Google has a more detailed explanation on the Google blog.
Forum discussion at Google Maps Help.