Given the scarcity of players...
Why would they not collaborate in advance - keep the auction price rock bottom and then sort out a private auction/exchange themselves?
Ofcom has drafted the legislation to open up two 4G bands next year, with bidders required to register by 11 December, the auction in January and the awards in June. The regulator published its proposals for the auction in August, but this is the proposed legislation which will make that auction happen. The final rules don't …
Because that would (by my reckoning) be classed as a price-fixing 'Cartel', which don't go down well at all with regulatory bodies such as the ECC. Just look at BA/ Virgin, or or LG/ Sharp/ Chunghwa:
http://www.theregister.co.uk/2008/11/12/lcd_price_fixing_guilty_pleas/