Freddie Mac officials confirmed last week that the GSE has launched a new pilot securities program as part of its ongoing effort to play a larger role in the burgeoning market of alternative mortgages. The initial deal, dubbed 05S001, is a $4 billion REMIC issuance backed by adjustable-rate mortgages with payment options. Although Freddie has bought some $9 billion in option ARMs so far this year, the recent transaction involves an $83 million class that…