Does anyone know (through specs or from experience) whether rerouting will take place, subsequent to the initial journey calculations, due to changes in the road conditions? Cheers...

Not automatically. You need to go to menu layers and switch on the traffic layer. There is then a button to re-route around problem spots.

The journey time calculated by Navigation, does however take into consideration any adverse traffic conditions en-route.

Not sure. I've seen first hand evidence of it picking the best route based on current traffic conditions, which is very easy to test (especially at rush hour!). Changing route based on traffic I have not seen, and it is very difficult to test for this. There doesn't seem to be any documentation that states one way or another.