[sitharus]

Yes, but you'd be better off using a higher voltage and switching DC-DC converters at the end.

The POTS lines would have ~50V on them in normal operation so they'd be insulated for 48V. However, V=I/R, and the lines have a constant resistance so if you can raise V and lower I you can get the same total wattage for a lower line loss. This is also why distribution networks are at 11kV and up.

Modern switching converters are pretty efficient, and you can also tailor them for the device so you don't have to double convert.

[Scoundreller]

Since you have 4 conductors to work with, you could run 12V for low-amperage applications and 48V for high-amperage stuff that justifies the switchgear.