The real question is whether an auction is the right thing to do at all. Whilst it is possible to design an auction that may allow an outsider to win, the likelihood is very high that the bidders who place the highest value on the spectrum will win. In other words, it's likely that incumbents (e.g. Vodacom, MTN) will win any auction, either to use the spectrum themselves (which, in fairness, is quite likely) or simply to prevent others from getting it (for two years).
Do you think ICASA has realised that this is the likely outcome? The only way for a startup company to win an auction like this would be effectively to bankrupt itself before it starts. Is this really what ICASA wants?