I am on Optus, can hardly use data on a moving train from inner west to city to north shore. Music streaming interrupts, gaming or video streaming is almost impossible. My signal is often H+ and occasionally 3G.
However, I often see people video calling or playing games on the train, are they all on Telstra?
I would have to know the specific train (and carriage) to be able to assess which mobile carrier those passengers were using.
Or, perhaps they have downloaded the videos / games to their device.