IP address blocks for out-of-band inter-provider links

[Sean Donelan <sean () donelan com>]

While working on how to set up an out-of-band communication network
between several providers, a question about whose IP addresses to use
came up.  The intent is to provide an out-of-band management network
allowing member providers to exchange management information and alerts
even if the main Internet is severely congested by malicious traffic.

Because this isn't supposed to be connected to the Internet, its not
necessary to use IANA/ARIN/RIPE/APNIC assigned IP address blocks. Several
providers use private addresses on their out-of-band management networks.
I would prefer to use globally unique IP addresses between providers to
avoid conflicts with the RFC1918 private addresses already in use in
provider's networks, and if the addresses accidently leak.

Other than exchange points, are there any other cases of unique IP
addresses being allocated for multi-provider purposes?