This is also a natural result of how much more pleasant taking rail is compared to driving. Sort of a induced demand and Jevon's paradox effect going on here.

Since you don't need to actively pay attention to the road you can multi-task, and that means that you can buy a house farther away. If there is no way to commute by rail, the house that you will select will need to be closer to your work, and will therefore likely be more expensive.