"It’s hard to claim that modern NYC subways wouldn’t use cylindrical tunnels had it not been for it’s predecessor. However, the technology for building steel tunnels, patented by Joseph Dixon for the Pneumatic Railway, undoubtedly was referenced by modern subway builders (Dixon)."
As far as I know, this is incorrect. The New York City subway tunnels are not cylindrical for the most part. Largely they are rectangular, built by digging down vertically from the surface, and then recovering the subway. (This technique is called cut-and-cover.) The subway stations which are in fact cylindrical stand out quite a bit, and are somewhat noticeable. For example, Clark Street on the 2/3 line is cylindrical. I don't know for a fact why this is, but I have been told that it is because construction of the subway station was done underwater using a circular drilling machine. Apparently it is cheaper to dig subway tunnels using a cut-and-cover technique, otherwise more tunnels might be circular.
None of this is to indicate that pneumatic tubes don't have mystique, merely that they don't appear to have been as influential as it is said in the article. --Ethan