I suppose instead of improvement, my rules are just a diversion from the standard set and possibly
extremely boring.

Although I really appreciate the grid result, some may not.
Thanks for that catch wlindley, I hadn't noticed that behavior before, but was able to reproduce it. As for the center tile for 3x3, for me it does populate but on the edges of a city sometimes it is not filled in. I don't have a current version of pak.britan at the moment, but I'll see if I can reproduce that also.
Fabio, is the center tile not having road access an issue? While visually more 'accurate' I thought all that really mattered was station coverage to catch the potential passengers or mail.
So if the grid is boring in your opinions, what would make city rules more exciting then? all diagonals? no streets?
While building these rules, I learned a lot and did create some other interesting rules by mistake.