Consider the following case study from Berk and DeMarzo's Corporate Finance.
My question is about the first sentence in the last paragraph:
Assume that participation in the swap was voluntary (as was claimed at the time), so that on the announcement the price of the existing bonds equaled the value of the new bonds.
How do we come to the conclusion that the price of the existing bonds equaled the value of the new bonds? I had thought that maybe we were arguing that each have the same underlying expected payout and risk profile and therefore the same price, but it's not clear why they should have the same expected payout when there are different promised cash flows in each case. I think perhaps it has something to do with the voluntary nature of the swap, but I can't understand what or why.