A press release from Foxtel today explains the change more neatly than I can rephrase it:
Previously iQ and iQ2 subscribers who did not have a connected return path installed were unable to order FOXTEL Box Office movies. Our technical team have changed the order signal to be sent via the FOXTEL connection rather than the phone landline. This overcomes the issue of ordering a movie without a home phone line and addresses the issue with subscribers who only have a mobile phone connection.
As people increasingly forsake landlines for mobiles and/or naked DSL, this is likely to become a more common scenario. Interestingly, while you can now order online or via phone even without a connected return path, you still need the return path if you want to order using your remote. But it’s a start.