Their rationale is that the recently installed signs erode faith in the system, create false hopes, erase the "mystery and magic" of the Subway and "threaten historical social behaviors, rendering obsolete the time-honored New York tradition of leaning over the platform edge with the hope of glimpsing headlights from an approaching train".
The rationale's absurd enough that it adds to the surreal implausibility of the whole exercise.
Reminds me of this: http://biphenyl.org/blog/2008/01/01/citation-needed/
(I was positive I've seen a mention of it in this blog, but google search shows nothing.)
The joke works better without the rationale.