I followed the steps in this thread, and am satisfied with the results:
Do it yourself License Plate Bumper Plugs
Of course I'd be happier if the dealer never put those holes there, but I can live with the plug solution. At least the color is the same right out of the package.
One of the vendors here sells a carbon fiber cover for the upper part of the grille that would cover the holes. I wish somebody would make just a flat black cover -- that would be the ultimate solution IMO.