How will Austria round up all those people? I'm guessing they will send out letters. How many immigrants will respond to those letters, and show up for deportation? I'm guessing zero.
So then Austria will either have to round up those people by force, or forget about the whole thing. If they choose the former, airports will become violent, chaotic places. if they choose the latter...then what's the point?
And one more thing. Suppose Syria, etc. denies those Austrian planes landing rights. Then what?
It’s the whole “four years” deal. They don’t mean to deport anyone. If they did, they would round them up and put them in miserable hell-hole camps on the state border, and tell them they are free to go outside of Austria any time they wish to any country that will take them.
When the “world” complains, Austria can tell their critics that if they really care about these people, come and get them. They are theirs for the taking.
Who wants to be on the flight crew for those trips?