Optus will be increasing their 3g coverage by the end of the year
yeah the optus yesG network is 900mhz which is not compatible with iPhone which only does 850/2100mhz.
Telstra nextG is 850mhz and the existing optus 3g signal you are getting is the shorter range 2100mhz in the city centres etc only.
Just waiting on AsA feedback which should be early next week (4th jul ish).
Sorry if I have to be vague but things are happening and as soon as I have a definitive result I'll post it up here with a more solid timeline.