are these miles usable on virgin australia?
Yes:
Upper Class: 270000 + fuel surcharges/fees
Premium Economy: 193500 + fuel surcharges/fees
Economy: 134500 + fuel surcharges/fees
And what other airlines are they connected to?
They're not part of an alliance, but
here's their list of partners.
(OT: According to
wikipedia, Branson says he'll be forming a fourth alliance, do you guys think this will increase competition, or complicate fragment award travel?)