I would not be surprised to find that the major problem here is that the 320 didn't advise ATC that it was holding short of the bay. It has happened a number of times around the world. If they didn't feel that they needed to advise ATC for some reason, the pushback clearance to the 737 should have alerted them to the fact that someone was pushing behind them & then they should have advised ATC.
Four points:
1/. If the push-back of Virgin was given as a conditional clearance then the fact that Jetstar wasn't clear meant that Virgin should have waited/paused/stopped before scrapping paint.
2/. Every day there are aircraft towing to a gate/bay that isn't ready, that is, there is equipment blocking access to the bay.
3/. Every hour aircraft are arriving at gates/bays where the NIGS haven't been configured or the marshaller isn't on-site. Why?
4/. The amount of unnecessary RT on ground frequencies needs to be addressed as a matter of urgency.