There was an escalator from the mezzanine to the lower level. It was in the extreme southwest corner of the mezzanine at 40th St. Sometimes it would be running on Saturday mornings, sometimes it would be off. AFAIK it's still in place, but the area where it originates has been walled off. Apparently the mezzanine extends beyond the tunnel entrance on the south end because the escalator doesn't cut through the active southbound platform. You can see it if you look to the right on a southbound A train just after it enters the tunnel.