I'm not seeing the contradiction in the first two statements. The emission comparisons are also regionally based. If your car emits the same as a 86 mpg car and 1/4 of the emissions of an ICE car in your region, then that just means the average ICE car in your region gets about 21.5 mpg (national average is 24.8, average in my region is 29).
As for localized results, they probably are just looking at the major players in each region. There are literally thousands of municipal power companies throughout the country when you take into account small town/city based power companies. The data from those small companies is probably in very few, if any, studies for them to pull data from. So a town like Turlock, CA is probably under PG&E numbers, even though they generate power on their own. Plus, even if those numbers are included, your local power numbers would still be diluted due to the fact they are likely on the national grid, so while you may have a local utility that generates power, it is still likely commingled with power generation from surrounding power utilities.
As for the numbers being the same for hundreds of miles, that is how the power grid works. Power is generated at the plant and transmitted to substations that in turn distribute the power to the end user. Substations can be up to 300 miles from the plant, meaning power generation from a plant is potentially transmitted 600 miles from end to end. Further, because utilities are always guessing at how much they need to generate at any given time, it is common practice for utilities to purchase power from each other when they come up short. There is no guarantee that the power that comes from your outlet was actually generated by your utility. Regions of 100+ miles are likely as granular as they can realistically get with the data.
Without signing up to see more about their methodology, one can only speculate on what data they use to generate the numbers for fossil fuel, but it is far from nearly impossible. There are lots of studies that track pollutants at all levels of oil exploration/extraction/processing/delivery.