Can built in TomToms work with the radio turned off?

[Repurr]

Hi,

My Dad has just bought a new renault scenic with a built in tomtom sat nav. He was told, which appears to be the case that the Audible speed camera sensor only works with the radio on?

Can anyone confirm this as it seems a little silly as Road Cameras still operate whether you have a radio on or off.

Also does anyone know of a workaround so that you can hear the audible sensor with said radio off?

Thanks

R