So none of them want their names to be public. So they government is unlikely to take action on Individual Basis on each black money account holder.
One alternative is Make the foreign banks with these black money accounts to invest the Black money from Indian unclaimed accounts back in to India.
The obvious question is why would a foreign bank invest even if the Indian governments asks to. The answer is the government can use its soft power.
Let me give you an example:
This is not something new. All countries use their buying power to get concessions.
If Country's burden of Debt/Interest on that debt decreases, then the same money can be used to reduce oil Price, reduce Tax or to give an extra meal to the poor.