Question: I'm interested in investing in power functions based trains, but want to automate switching points. Is this possible? What is the cheapest / easiest way of achieving this?

Answer: 
There is a pure way of changing the points at a track. It requires as few pieces as you like: a motor and two technic beam/bricks. This [video](http://www.youtube.com/watch?v=WoNiq5FCd9U) demonstrates the principles of point changing with a NXT motor and will work with PF and RCX.

[![enter image description here](https://i.stack.imgur.com/fL1F8.png)](http://www.youtube.com/watch?v=WoNiq5FCd9U&feature=player_detailpage#t=35s)

You can use Mindstorms to program the events that trigger the points to change. It will cost you extra, but there are benefits.
I just found this link on another forum.

This is a set of instructions for using a medium power functions motor to switch the point. It is quite compact and is compatible with the infrared receiver. 

(page 7 of 8)
<http://www.flickr.com/photos/whoward69/3731639719/in/set-72157621512518259/>