I believe that it is sometimes appropriate to direct SDO's to the IAB,
and perhaps more often more appropriate for individual ADs/WGs to form
the relationship and then
prod the IAB if formalization is needed.
In either case, everybody keeping everybody else apprised
is important...
Which probably doesn't answer Andy's question, and perhaps
suggests there should be "IETF meeter greeter"?
..... I think the IAB chair, who directs the entity responsible for
external relationships, has to have this role, and keep track of who talks
to who........