The max input voltage of most linear regulators is 27V or lower, and in general you don't want to
use linear regulation of efficiency grounds.
There are DC-DC converters with 48V rated inputs which would be more useful and able to get
more sensible currents out of 48V phantom power (which is limited to a few mA IIRC, something
like a 6k8 series resistor is used).
You want to choose a low quiescent current converter though to avoid wasting any of those mA,
and you will be limited how much power is available to the load circuit.