When Hooky DJ'd in Hackney last year he mentioned that the Freebass album, the remaining tracks from the Siren's sessions and his Hacienda book would all be released around the same time. While the time mentioned (spring) has slipped, from a promotional perspective that makes a lot of sense, so no reason to believe that approach will change.
So right now, from what info is out there, I would guess a Q4 2009 release date for these items has to be a possibility.
When upcoming releases get leaked it's usually just before the official street date cos the source is typically a promo copy. Quite often it's someone in the media who has received a promo for review purposes and is careless with who they hand it off to or upload it themselves. That's what happened with Sirens - an American journalist's promo copy got hosted on a P2P site. Before promo copies are issued (a month or so ahead of the official release), it's very unlikely an album would get leaked so I can't see anything negative to take from a lack of a leak.
I know of one person in the media who has heard the remaining Siren's tracks and thought they were great. The track Ally mentions, from hazy memory, was quality. No doubt Warners are also discussing a release schedule with the band themselves and that could be driving the time scale as much as anything e.g. is Bernard thinking about playing some of these new NO tracks on a forthcoming BL tour? or do they want clearly staggered release dates so one doesn't overshadow the other?. Er, fcuk knows.