wired tomtom5 on xda IIs

Hi All,
Apologies if this has been asked before but here goes.

I am looking to possibly install a wired TomTom 5 kit onto my xdaIIs. I have been running the xda without the o2 active interface for a few months now and have found it to be a far more stable platform.

My question really is "What happens to TomTom when the phone rings"? does tomtom shutdown, or stop giving out voice instructions or does the screen switch to the phone display? What actually happens?

I would welcome any feedback regarding this setup before I splash the cash and potentially regret it. Also, where does the receiver plug into the xda as I use a cradle which effectively blocks access to the bottom of the unit. The cradle has a square-ish input to one side which I am hoping I will be able to plug the gps lead into.

Hope you can help,

Stuart