Maybe they always work this way, set the budget and release date in stone, the devs work until the budget/ time runs out, dlc released in whatever state it's reached. It would explain why we don't go to Bishop Auckland on the Tees Valley and why there are unused freight locations on the Tees Valley map, namely Darlington Rail Maintenance Yard and Saltburn on Sea. Unless a future release will use them. The line to Stockton-on-Tees is modelled but fizzles out before getting there. Was it going to be the Stockton and Darlington Railway? Who knows?