When I first saw Hartland’s Interurbans I noticed they looked amazingly similar to early IRT Sbway Cars. These were New York Cities very first subway trains. Here is a link to a photo: http://www.nycsubway.org/perl/show?6874.
The Hartland cars would require removal of pantographs, a new paint job and additional doors on the ends and in the center of the car body. They should be painted pullman green. It would be nice to see some Subways in G scale as they are very popular in O.[