It is kind of a wash. As an accountant, it appears like a deal that means $5-10 million on a present-value basis to AGO. Of course it all depends on how much time is left on the assumed underwritings/policies. RDN's stock is up because of the improvement to their capital to risk ratio. I am sure that AGO analyzed the underwritings and assumed them fully understanding the quality.
It looks like this transation cost AGO nothing and actually they make a few bucks at closing which increases their adjusted book value from $48.87 to $49.24. In addtion they will also receive $108 million of unearned premiums which they will get to book into income over time.