They're likely deploying the same Cisco gateway that cox is deploying in the US. The gateway is supposed to be able to convert the QAM signal into IP in real time and shuttle them to IP only devices. If they flip the 4642s into IP only mode, they should be able to pause and rewind live TV. But at the same time, each home would be limited to 8 live streams.
Also the fact that they list recording up to 8 shows and storing up to 240 hours of programming as the only Nextbox 3.0 exclusives leads me to believe that it will run the exact same interface as the current NextBox 2.0.
EDIT: It looks like Ciscos new 9800 series only supports 6 tuners, so perhaps Rogers is gearing up to dump them for another vendor or they've got Cisco to make a custom model for them.