In fact, 10 of the 17 banks tracked by Inside Mortgage Trends posted increased mortgage-banking income during the final three months of 2013, and all of them reported a positive showing.

The market produced $4.94 billion of new non-agency MBS during the fourth quarter, according to a new Inside MBS & ABS analysis and ranking, the weakest output of the year.

A key factor in the upswing in private MI share of Fannie/Freddie business was the relatively steadier volume in purchase-mortgage securitization compared to refinance loans.

Refinance mortgages accounted for 80.1 percent of agency production back in 2012, but that declined to 65.6 percent last year and just 45.3 percent of fourth-quarter business.

The megabanks no longer have a total "lock" on the MBS issuance market. But is this trend short-lived?

When it comes to doing business with Fannie Mae, Wells Fargo's volume is almost three-times that of its closest competitor, Chase Home Finance, IMF found.

Monthly production of single-family MBS went into a steady, year-long decline at the beginning of 2013. In December, total single-family MBS issuance fell to just $77.1 billion, the lowest monthly production figure since July 2011.

Freddie Mac reported new buyback demands on $3.3 billion of mortgages during the third quarter, a stunning 31 percent increase from the previous period.

As an industry, banks assigned a fair-market value of $48.4 billion to their mortgage servicing rights, according to figures compiled by Inside Mortgage Trends.

The amount of outstanding mortgage-backed securities increased again in the third quarter of 2013.