Moving from A to B efficiently

How would I move a camera from point A to point B by the most efficient route?

I'm working on building a housing estate and would like the user to be able to select a particular address and for the camera to move along the streets to reach that address.

Sounds like you're looking for 'pathfinding'. A standard solution for this is A* using a grid, navigation mesh, or waypoint system to represent the search space.

There's one or two pathfinding libraries available for use with Unity that you could probably use for this. Also, searching here and on the forums for 'pathfinding' or 'waypoints' should lead you to some useful references.