the neurocrit people aren't generally being hired to work solely in NICUs -- you are right, there are not many non-big-academic-medical-centers that have those. The neurocrit people in private practice are being hired mostly as neurohospitalists -- presumably some proportion of those will be "neurocritically" ill.
Neurointerventional is a whole 'nother bag of worms that I'm not too up on so I won't even pretend to know . . .