So all carriers are capped at 20Mhz of 700MHz spectrum. Which...

So all carriers are capped at 20Mhz of 700MHz spectrum.
Which means Optus will be capped at buying 10MHZ.
But for Vodafone or TPG the economics of running creating a seperate 700MHz network with only 5 MHZ will be financially challenged. New entrants will need 10 MHZ at least.
Optus has been on a huge expansion plan and now has 1100 more 700MHZ towers than Telstra.
Optus needs to expand its bandwidth by 10MHZ to match Telstra's data speeds.
If Optus does not buy the spectrum it will always have a second rate network
The last thing Vodafone Optus or Telstra need is TPG getting 10 MHz. Interesting times ahead