It is self funding and what Minto said is accurate. But sustainable, no. Teachers used to be underpaid but with the promise of a lucrative pension. Under labour teachers have protested for salary increases. Today they have very reasonable pay for their work. Their pension system has not adjusted to reflect this.
The teachers of today have to pay for the teachers of yesterday. This is not a sustainable scheme. As people live longer the pension demand is going to out grow the funding potential of today's teachers.
As long as a realistic value for life expectancy is used.
Half the Torie's calculations are based on the assumption that people will live to 105 average within 15 years.