Essentially there's the option for users to pay for phone calls and Internet, but I can see Telstra being far more interested in the 'sponsored services' method. In a public setting such as a food court I can see this being popular.
A quick scenario:
Lets say your having lunch with a mate and you mention a website they should check out. Almost all of us have the option to use our mobile to view it, but in reality looking at anything more than a basic website on most mobiles isn't exactly spectacular - especially when more than one person is viewing the same screen.
10 metres away you see a Pie Payphone with a large screen and a small banner reading 'Free Internet', so naturally you take a look. You enter the address and view the website, most likely viewing a brief advertisement from the 'sponsor'. Simple.
Although its only a brief transaction the terminal has a captive audience resulting in a win/win for both parties. You get to surf the Internet (free) and the sponsor has a wide, captive audience with a reason to view the advertisement (no time for a toilet break!).
You can see why Telstra is interested, this payphone is an entirely new advertising medium and companies pay BIG money to make their name known.
I should mention I only bought in today @ 3.1c after much deliberation, the original plan was to buy in on Monday (doh!) but work got in the way :/
NWZ Price at posting:
3.2¢ Sentiment: Buy Disclosure: Held