The setup:
Transport carrying troops is surrounded on all sides by one line of infantry in melee, and it gets destroyed. The space between the surrounding infantry bases is around 1.5
cm so no room for any enemy model disembarking to move through. According to the
BRB page 211, one bullet point states:
"Disembarking units must be set up wholly within 3" of their transport and not within engagement range of any enemy models"
and the other:
"Units that have disembarked count as having moved this turn."
So, can the units inside the transport "teleport" within 3" of the destroyed transport (and further than 1" of the enemy models), "teleporting" over the surrounding infantry units or because of the second sentence, them counting as having moved, it is implied that they have to MOVE to their new position, which is impossible, because according to the movement rules, no models may move through/over enemy models (unless they have fly).
In which case, if the transport was carrying units with fly, they could "teleport", but if no fly, sorry you go down with the transport because you can't disembark (Emergency disembarkation stratagem doesn't help either)?
So disembark for everyone or no one except fly units?