Well, I just played with sshnet and looked at the source.  It only gives you a /net/cs and
a /net/tcp.  ndb/cs in this world is a bit minimal.  Unless your factotum is also started
under that network, it shouldn't be able to dial auth servers available only under that
network.  You might try starting a second factotum.  However, then it probably won't be
able to figure out how to map the authdom to an auth server since that isn't available
via the sshnet cs.

I don't see a way around this without rewriting code.  If the sshnet cs simulation
actually looked in your /lib/ndb or if authdial looked in your /lib/ndb files after
not finding things in /net/cs, you'ld have a chance of making it work.