So basically urban areas get more channels because the new tech uses less spectrum and everywhere else gets less because they will no longer be able to listen to the channels physically located in urban areas that they could pick up using the old tech.

Does the new tech make bandwidth sufficiently cheap that more stations can broadcast their content on multiple frequencies in physically separate locations(which is not uncommon for large FM stations to do today)? If so you'd basically get the same coverage using less spectrum by broadcasting the same station from more sites using the newer tech (not that this would happen if the initial investment in the physical equipment is anything large enough to cars about).