They sure can! But it won't help CET-1 which is the mandatory requirement that needs to be met in order for the GSEs to be released.
Wouldn't it be silly to sell Jr. Preferreds that don't help recapitalize the GSEs?
It also means they would have to start paying Dividends immediately on all of the Jr. Preferreds, further depleting much needed capital from the GSEs :-(
I'm glad the GSEs have retained Advisors to help them so some of the FNMA Fantasy suggestions can be put to rest.