There's some footage of the actual prototype here http://main.wikispeed.softlaunch.352media.com/car

They're fairly large claims but within reason, some years ago VW build a car that used 1L/100kms which styling wise is similar to this one but a bit smaller and with a diesel engine. I think they called it their 1 or something like that. SO I don't think it's unbelievable but yes, it would be good to see some verified results.