According to 22.214.171.124.10, vehicles may freely pass through enemy-occupied spaces, as long as they don't end there.
1) What happens if, due to opportunity fire, a vehicle is damaged/immoblized/suppressed/broken such that it is unable to move out of the enemy-occupied space? Should we follow the same rule as for overruns (126.96.36.199) - the vehicle goes back to its last hex?
2) What about weird corner cases where the vehicle has passed through multiple enemy-occupied spaces contiguously, does it go back all the way to the last unoccupied space (possibly going out of LOS of the unit that shot it in the first place)?
3) How does coexistence work with non-vehicle units? Can vehicles move through enemy non-vehicles? Can non-vehicles move through enemy non-vehicles? Can non-vehicles move through enemy vehicles?
1) Yes, just like Overrun.
2) Yes, it would need to go back to the first entry hex. That's a weird case, but there isn't any other straightforward way to resolve the situation.
3)It works in the exact same way. The very beginning of the Advanced Games rules states that, "When reviewing the Advanced Game keep in mind that all Basic Game rules still apply."