They are as good and any chicken for foraging.
It is hard to keep a flock going with just foraging in a city though.
my silkies are not good at foraging while my araucanas are. I had egyptian fayoumis for a while and they kept escaping and almost lived by foraging. they preferred what they could find in a neighboring plot. unfortunately they were not safe there so I sent them to a friend's farm. as I will move to the country I plan to keep fayoumis again. I read about pita pinta chickens and they say that pita pinta prefer to forage - sounds like fayoumi. I'll have 2 acres in my new place.