With our 3 car fleet (4th car is not finished yet) running on propane keeping the tanks filled is the one drawback. Propane filling is not self service, so there is waiting involved with getting tanks filled. I don’t see self service as a possibility, there is too much potential for a careless splash of propane and liquid propane is very cold, it will immediately freeze damage tissue, a freezer burn.
I am a little surprised that they expect only a 20% reduction in greenhouse gas emissions. I am under the impression that the reduction is greater than that. I am planning to have an emission test someday on one of my conversions to see what the emission levels are.