Unfortunately it's not just a switch as most grid tie inverters have a protective circuit that is integral with the system. It can't be bypassed as the parameters are burned into the eprom or at very least set by software that the end user has no access to. Likewise, no "switches" it's all solid state. The inverter will look for a narrow band of voltage coming in from the grid which by itself would be easy to overcome. The hard part is frequency. The system also looks for a perfect sine wave of 60 cycles per second, give or take maybe .05 hertz. If an outside power source is making 59.94 hertz or 60.06 hertz it locks down the system. Not many generators are that precise. Also there is the problem of what happens when say 42 panels start feeding back into a 600 watt "pilot" generator at, say 10,000 watts. I don't pretend to know the answer to the last one.
If there are any electrical gurus out there that know how to get past those hurdles, especially the frequency one, please feel free to jump right in.
I'm not talking about a switch on the inverter, I'm talking about the main power entry panel to the home. There HAS to be a way to isolate the house from the utility line to allow people to work on the house power circuits. Any electrician who would work on such a system without a MECHANICAL isolation switch WITH A POSITIVE LOCKOUT is an idiot. I know "I" damned well wouldn't trust an "electronically controlled" switch as sufficient protection.
And anybody who is so stupid as to buy a solar power system that DIES when the grid goes down deserves whatever consequences happen to them as a result.