Well sounds like the rationing shouldn't be an issue for rental cars going forward. I believe as of tomorrow, only New York City will remain on the Odd/Even schedule, so anyone should be able to fill up in NJ or Westchester or Long Island and still end up in Manhattan (or wherever) with a near-full tank of gas.
^
FWIW, I never fill up in Manhattan, and rarely within NYC limits.
I suppose this could remain an issue for the car-sharing services.