What is the tax status of assets recovered via bankruptcy proceedings?

Say someone held some non-cash assets (shares, cryptocurrency, etc.) with a third-party business that went bankrupt. They become a creditor in the bankruptcy proceedings, lose access to whatever assets were being held on their behalf, and may at some point in the future recover some fraction of their original assets (usually but not necessarily as cash). My question is basically, what is the tax treatment for any assets recovered (assume US jurisdiction, though also the Australian case would be interesting)?

As in, do they count as legal winnings/compensation (not usually taxable), regular income, short/long-term capital gains, or something else entirely? And can the portion of assets lost/not recovered be written off against the amount recovered (if the recovery is taxable)? And if so, is that done based upon the value at the time of the bankruptcy or the "on paper" value at the time the recoverable assets are returned?

As a concrete example, say someone purchased 100 BTC on mtgox.com back when BTC was trading around $10 a coin. If they held all their coins until the exchange went bankrupt, they’d be looking at recovering somewhere around 20 BTC, probably sometime next year. When that happens, the value of the recovered BTC could exceed $1 million. Far more than the initial investment, but also far less than the present value of the 80 BTC lost in the bankruptcy. Is the tax payable:

• Nothing, because the assets are coming from a court proceeding?
• Nothing until the BTC are converted to fiat currency, then the converted amount is treated as capital gains?
• Nothing, because there are 4 times as many "lost" BTC that can be accounted for as a loss?
• The full value of the 20 BTC recovered, as income?
• The full value of the 20 BTC recovered, as capital gains?
• Something else?

And is the outcome different if the recovery is made in cash/fiat currency as opposed to BTC/cryptocurrency?