jonkey - forget spending the dividend on infrastructure. Borrow an amount that can be serviced by the dividend - i.e. over $6bn. It's more than the government will raise by flogging it off, and will be able to increase over time, as health insurance grows (and Medibank matures as a lean organisation).
If they did an IPO for $5.5bn as suggested by ddzx, I'd be happy they'd raised enough.
$4bn and less - that's arbitrage.
