On this site, there is a list of crayon rail games FAQ and accompanying answers, presumably from Mayfair games. I don't want to doubt the authenticity of that list. Rather, I'd like confirmation that the information given in there really is from Mayfair Games. Ideally, I'd like an FAQ from an official source, but confirmation that this is really from Mayfair would work.
There doesn't seem to be any information about why the FAQ is being hosted at the fan site, and not at Mayfair Games itself, but there are several circumstantial pieces of evidence.
For completeness, I did do some digging in the Internet Archive for a FAQ from 2008 hosted at Mayfair Games, but found nothing.
Interesting question. The linked FAQs look detailed and helpful. Now I'm curious as to why you require proof of provenance.