Here ya go:
http://forums.windowscentral.com/windows-phone-8-1-preview-developers/277131-how-do-i-get-cortana-show-me-my-commute-my-way-work-my-way-home.html
It's all predictive; Cortana will learn after a while that you leave HOME at a certain time and leave work at a certain time and will notify you.
