Fannie Mae seller/servicers also can dodge the maintenance fee if they have $25 million in Fannie servicing or paid $5,000 in technology fees.

Besides Citi, a handful of large depositories are in the midst of wrapping up sizable MSR auctions this week, including offerings from Wells Fargo and Flagstar Bancorp.

Citadel Servicing CEO Dan Perl said "the phones are ringing like a son-of-a-gun" at his nonprime lending shop.

The jumbo features that Moody's worries about include super senior support bonds, exchangeable securities, principal-only bonds, and pool interest-only bonds.

The talk has prompted speculation that the FHFA could lower the conforming loan limit to $400,000 or, as conservator of the GSEs, direct them to reduce high-cost loan limits.

Over the past two years, upwards of $1 billion has been raised by private-equity funds seeking to buy servicing rights in the secondary market.

Loan officers, so far, have been spared the layoff carnage, but that may change depending on where volumes wind up.

The firm estimates that upwards of $300 billion of MSRs are currently on the auction block with another $1 trillion to $2 trillion to come.

Nationstar's new filing with the Securities and Exchange Commission offers little in the way of information on the terms of the new $1 billion facility.

PHH saw its share price spike late last week after rumors spread that it may sell a large block of mortgage servicing rights.