Please forgive my speculation, but would it not be fairly easy for the GPWS/TAWS to have been MEL'd at some point on this sales excursion, particularly since the aircraft isn't engaged in public carriage? That would also explain the picture of the aircraft's overhead panel, taken on the ground some time prior to the accident, with the TAWS - Terrain button clearly indicating "OFF".
I know it's quite a logical leap, and I'm not at all familiar with this particular aircraft type, but is "GPWS/TAWS switch OFF" part of a normal on-the-ground procedure for anyone here who flies modern jet aircraft? I'm trying to remember if it's ever been a part of my flow/checklist on anything I've flown, but I'm drawing a blank
(edit: The photo in question, TAWS switches on the left hand side, close to the top)
