Could you attach it to a smartport configured as AC Coupled Input though (Assuming the inverter handles the AC sync)? Would the GB remain powered (or power up) if the only AC input was from a smart port configured as AC Coupled input?
What I'm really looking for is a cold-start option for the GB that doesn't have a FB/1xkPV installed yet but does have a generator with 2 wire. I want the GB to stay online long enough if the grid goes down to crank the generator up so I need a way to maintain power to the GB brains long enough to make that happen.