I don't know if the N95 is a NextG compatible phone. A NextG sim will work in it, however once its out of GSM range you might get into trouble. Most guys I know up here have either a Samsung SGH-A411 or SGH-A412 (the 411 is the prepaid version, the 412 can be bought outright or on a monthly plan, otherwise they are the exact same phone) which is a country "Blue Tick" phone meaning that it has far better coverage in bush areas. I got my 412 for about $110 not too long ago on eBay and has been well worth it. Either way, you'll actually need a NextG compatible handset (meaning it uses the NextG network, not the GSM network) as telstra is only providing NextG out on communities.
So far I've gotten mine to work on the ground at YBTI, YSNB, YGPT, YCKI, YGBI, YELD, YRNG, YMGB, YMGD, YPGV, YGTE, YNUM, YNGU, YBRL, YMHU, YTNK, YPTN, YBCR, and obviously YPDN. The better part is that I've been able to get coverage at 5000' in most areas, and coverage at 9500' pretty much everywhere. Coupled via bluetooth to a lightspeed and its great if you lose your radio, need to submit a flight plan amendment, need to contact your destination or even company ops while out in the sticks. Have even taken charter bookings while in the cruise which is far better than having customers diverted through to message bank.