I second the experience that import -r DOES work for me, and
was I happy about that discovery. It meant yarn would suck in
an ASCII file in SOME form and I was not restricted to the SOUP
packets.
As one benefit, this is my preferred way to send a set of
news articles on a subject of my choice to yarn: I use the trn
mail program's excellent pattern matching facilities to pick
out a set of articles within a newsgroup that have pattern ``XXXX''
in their header/body -- etc. I dumpt these articles to a mailbox
type file. Then I import the file with import -r.