The only problem with the mechanical interlock is that
you don't know when power had been restored ...
no street lights here, but I did happen to see a light in
the neighbor's house, but that's pretty far away. BTW, there are
"reverse alarms" available to detect power returned and sound an alarm.
I have not installed one of these yet.



" Power-Back "

https://www.amazon.com/Reliance-Cont.../dp/B003KREORA

I just installed one last year - no problems -
and the screeching loud noise would probably
even wake me in the night.
Keep earplugs handy to get to the panel to turn it off !
... it's painfully loud & an awful screech.
John T.