This aircraft isn’t very big. These types of regional puddle jumpers are only useful when connecting to major long haul aircraft, which is only really possible at large airports.
> justify an extension of the Red Line
It's obvious that even with small electric aircraft, there would not be enough traffic to justify the expense of rail expansion. However, point-to-point air flights would increase the economic viability of many small cities without the need for hub airports. For example, I was driving for business for a while to Burlington, Vermont. I would have welcomed a small puddle jumper from the GA airport 5 miles away to Burlington instead of having to drive to fly out of Logan. It would've been more expensive than driving, but it would have been more enjoyable since I'm the kind of passenger who leaves nose prints on the window. Flying from a local airport to Ithaca, New York (partner's family) would be a viable replacement for driving 6+ hours.
Many more possibilities become practical once you free yourself of the hub and spoke model and combine it with economical electric aircraft.
Highway self-driving is going to come. And highway self-driving will probably replace the regional flight. If I could sleep in my car to get where I was going while I drove me on highways overnight, it would probably replace all airline flights less than 800 mi and probably more.
You get to leave whenever you want. You got to take a far larger amount of baggage. It gets seriously cheap for a family. You can stop away along the way to rest. The seats are more comfortable. And when you get there you have local street transportation. No need to rent a car.
A self-driving RV van and the sprinter class or something like that makes it even easier.
If you use GA airports near more prominent cities, using rail transit to get to nearby larger cities is worth the disruption. For example, with these aircraft, BED would have enough traffic to Boston to justify an extension of the Red Line through Lexington and Arlington.