I think there's a bit of uncertainty as to the type of fixture and the circuit powering it.
Hotline, I think you are imagining one of those 'bug eyes' that only trun 'on' when the power fails. I agree that HID would be a poor choice for those.
I was thinking of a separate circuit that, in addition to the usual power, also had back-up power available (either within the fixture, or serving the entire circuit). In the later instance the light would operate as any other light- on at dusk, etc. The difference being that the light would remain 'on' if there were a power failure.
