Not sure what they used to do the routes layer, but I suspect they used Gigapan hardware and software http://gigapan.com/
Think you have to buy the hardware to use their software. If you want to experiment you could start with this freebie from Microsoft: https://photosynth.net/default.aspx
If you make progress this open source viewer might be useful: http://iipimage.sourceforge.net/
Coincidentally stumbled across it today whilst looking for something else.