I was able to install this on my 2014 prius plug in base model. I did this whole thing without unplugging the 12V battery. Some notes that I think would make it easier for plug ins. I was able to buy one for 2nd gen prius and it worked on my 3rd gen plug in. Mine came with a harness that had the wires cut. I simply attached 3 wires, soldered and electrical taped them. My stock mirror that came with my car, people say just pull upwards, actually there is a little button on the bottom, you have to push it inwards (towards the cabin) with a big flat screw driver, before pulling up on the mirror. The ground and constant 12V you tap from the overhead lights as indicated in the PDF manual file. So you actually only have to route 1 wire through the headliner, down the driver side pillar and behind the outside mirror control button. To get access to the outside mirror control button, you pull the left kick panel from the top enough so you can get a screw driver in and remove the 1 screw out (careful not to drop behind the kick panel. Once that one screw is out, you simply pull the panel off but not too hard because it is still attached to the hood release cord. Unclip the 10pin outside mirror control and tap into the grey wire for 12V ACC. hope that helps.
