This seems brain dead. I think the intent of 1597 was to say here
are some numbers you can go play with privately. Since they are
private they should never appear on the public Internet, anywhere,
ever. If any router on the public Internet sees a packet to (or
from) a 1597 network it can throw it in the bit bucket and forget it.
What is public and what is private? The only thing that private can
mean given the text in 1597 is that it doesn't have global significance.
If I make an agreement with a "public" SP to use 1597 addresses, or if
two SPs to use 1597 addresses, by your definition, they are not private,
but I claim that by local agreement, they certainly ARE private and
fulfill the definitions of 1597, if not perhaps the original intent.
It would be possible for some private experiment to use some 1597
addresses to exchange packets over a "wire". Such a wire could be
implemented by some pretty complicated arrangements with conventional
public Internet service providers -- but any packets with 1597 addresses
would have to be encapsulated inside packets with acceptable addresses
for the public Internet to go through public Internet exchange points.
Obviously given the difference of opinions, we're not going to see the
following corallary in the same light, but...
An IX, and in particular, an RA-administered NAP, should support whatever
routing policy has been contracted between the RA and the customer(s) of
the RA. If two customers routing policy include sharing a 1597 network,
that is something that needs to be considered.