Warren,
The UUCP map data from comp.mail.maps is a two level format: one for pathalias(1)
and the rest for various programs. Pathalias will ignore any line beginning in
'#' - those are comments to it. Some of those comments have a format
specification which other programs can effectively grep for and parse.
So, yes, you can add or modify any line beginning in '#' - pathalias won't
care.
Given the Google archive of comp.mail.maps, you can pick your snapshot of the state of the
UUCP network. The last one seems to be 1998.
Erik