Matt,
Those beige buildings that you are seeing Normally house some kind of DLC. That is a digital line concentrator. It was in earlier times used to terminate T-1 lines to a multiplexer for the purpose of bringing 24 DSO(talk circuits) to a neighborhood on one DS1 (T-1 circuit). This would relieve the number of individual cable pairs needed to supply an area with the needed number of lines. These buildings are now fed with fiber optic lines which greatly increases the number of lines concentrated. For instance in an OC 3 fiber circuit, twenty-eight T-1's are supplied to the neighborhood. You do the math from there. Fiber has been increased since I retired from the business. Now Optical circuits come in OC-3,OC-12 OC-48 OC192, and many more breakdowns available through DWDM. That is dense wavelength digital multiplexing. This is possible due to the different available frequency ranges in the light spectrum.
This is basic line concentration 101.

Al

Al