A work of the United States government, as defined by United States copyright law, is "a work prepared by an officer or employee of the U.S. government as part of that person's official duties." The term only applies to the work of the federal government, not state or local governments.
The MTA is not a government agency in the sense of the Department of Defense. The are a public-benefit corporation in the sense of the postal service or Amtrak. Though they draw money from state and city raised taxes. In other words, it's arguable whether government publication laws would apply to the MTA.
Which is a reason not to rely on such feeds without a fixed-price contract in place. I passed on an app idea where the feed provider could potentially release his own app and shut me off if/when my app becomes popular. The feed provider refused to enter into a contract, and still has not released his own app after 8 months - depriving himself and his users of the service. Pity.
Maybe an interesting question: what if those schedules were hard to make? e.g. they resulted from an expensive analysis of a traveling salesman problem.
But additionally, aren't publications of the government by law automatically made a part of the public domain?