As a baseline data point, my Honda Insight gets 3.3 l/100km

Is that factory data, or your experience? Is it an average, long-distance or city traffic? What it certainly isn't is primary energy consummption (though I guess the refinery correction would add only a few tenths). At any rate, even with two onboard it compares to the posted figure for trams and subways.

That's my personal experience. It's 72.3 miles per gallon averaged over about 20,000 miles. Lots of 70 mph highway driving, air conditioning, winter snow, plus city traffic, etc. Mostly with only one occupant.