ATC has no authority on the apron;
The 'Approval' is for the aircraft to push in order to access the taxiway, not to pushback because it is clear behind.
Why then don't we say "intending to pushback" or "request traffic for pushback" instead of "request pushback"? ATC does have part-responsibility in this scenario. If it passed traffic to the Virgin on the Jetstar then fine.
From a staff utilisation perspective, it is rational not to use Engineers, they are simply too expensive for such tasks
Economic rationalism is great...right up to the point where that winglet knocked the tailbit off.