You can now put a landline number (01 or 02) on to a mobile phone and use sip/internet to make and receive calls. The main benefit is reducing the cost of international calls – either to a mobile abroad or from a mobile abroad – but also if you tend to use your mobile phone when calling from your office location.
As far as the call routing is concerned, it is a local/national call rate. Currently, this application is only available on limited handsets but this will change.