I am just through planning a trip on Google Maps, and like you, I've been trying to find outlets to charge from through Google Street View. What I have been finding out in my regular e-riding and charging out-n-about is Gas Stations are easy to find outlets, pop/ice machines, older mini strip malls, car washes. I have traveled through Europe back in 2007 by bus and train, but was never on the look out outlets as I am now. Only been ebiking for 2-3 yrs now.
Looks like Google Maps has quite the data for the Alps.
https://www.google.ca/maps/place/Alps/@46.9890244,11.5434725,604062m/data=!3m1!1e3!4m5!3m4!1s0x4789459fb534be51:0x38c7fdcd674c57d!8m2!3d46.8876191!4d9.6569996
Interestingly enough Austria and Germany are quite void of Google Street View data.
Just go through your planned route in the Street View mode and have an eyeball on outlets.
Another option that I thought about today as I was hunting down an outlet, is to be able to easily remove your battery pack from the bike, so you can hunt down outlets in a restaraunt, fast food joint or something.
Scanning some random small town, it took quite a long time to find an outside outlet.
https://www.google.ca/maps/@46.9425693,10.3595817,3a,38.6y,39.46h,84.15t/data=!3m6!1e1!3m4!1s40Me5uFxCqLmh6ogxQZT_A!2e0!7i13312!8i6656
Cant find much for outdoor outlets. Thats the only one I've found, if its even an outlet. Been searching gas stations.