This is the way I see it.
You have a house that you no longer can pay because you were greedy and didn't want to rent an apartment that you could afford. But let's leave that discussion for another topic.
You owed the bank $300,000. Since you couldn't sell in short sell and didn't have a leg to stand on, the bank made you an offer that you could not legally refuse. The bank offered you $100,000 based on the market value and took your house. YOU NO LONGER HAVE A HOUSE.
If you file your taxes and report $200,000 loss. It is a personal loss, no need to mention it on your return.
If the bank sells the house for $125,000, you have a cancellation of debt of $175,000, which according to the code it is taxable unless you are insolvent. You are tied to the papers you signed when you purchased the house and to the IRS code. The paper said that you were personally liable for the debt.
If the bank sells, your former house for $700,000, the bank will report $400,000 capital gain or ordinary income on its return and will not issue you a 1099-C. Remember that at this point, you don't have a house and therefore you cannot have a profit. The house went back to the bank and only the owner of an asset can benefit from any profit.
To answer original question (since no one tried to):
If it was pure rental, you dispose the asset on a loss for 2010. Claim the loss and report 1099-C the year it shows up.
Technically you could report everything in 2010: The disposal of the asset, the loss on the rental asset, and the cancellation of debt. For matching purposes, you should report the cancellation of debt in the year the 1099-C is issued by the bank.