Generally if the delays are 20mins or more they are passed to the aircraft much much earlier. Often times in this case aircraft will be told something like expect holding speed reduction approved
Yep, works quite well. I've actually been told to expect 20mins + delay into Perth when taxiing somewhere up in the Pilbara. Simply climb and cruise at min speed, stay low and you can absorb the majority of the delay. Thankfully days like that are pretty rare these days and usually weather related (although it's getting to that time of the year again!)