28 secs to 40 secs sounds very much like a track from Craig Armstrong's score to 'Plunkett & Macleane' (the track "Hanging"). Could be a licensed mix, it's happened before; ie Clint Mansell's "Lux Aeterna" from his score to 'Requiem for a Dream' was mixed later for use as a trailer song for 'The Two Towers'. This could also be a track from a trailer music company like Immediate or X-ray Dog (in which case, check
http://www.soundtrack.net/trailers periodically, eventually the song will be identified and listed there).