> Northern Territory imposes a distinctly unchallenging top speed of 110km/h.
As of 2009, the NT limit was 130 km/h: still fast enough to be challenging for even the fastest cars (though you do have to slow for towns, including the 40 km/h school zone in Tennant Creek). South Australia, OTOH, is indeed 110 km/h (less in towns).
> There are towns and road stops every 100km-200km.
South of Alice Springs this may be... optimistic. Get a copy of the route notes. Each team will be given one at the meeting one or two days before the start; keep an eye on the notice board at Foskey Pavilion. Or they may join the 21st century and publish the route notes online.
Best phone coverage is via Telstra's Next G network, which is 3G on a lower frequency (850 MHz) so the cells reach further. It's proprietary to Australia, but you might be able to pick up a phone and/or wireless internet dongle for it at a reasonable price.