I wouldn't see why not. Many gamebird farmers use Silkies as natural incubators, so I wouldn't see why it would be any different. You would probably have more luck with them adopting the eggs if you place them under the hen at night.
I just had a bantam frizzle cochin hatch a RIR and an EE. Still 6 more eggs to go, so hopefully we get more. Only 2 of those left are frizzle eggs.
My serama is sitting on 7 eggs - one of them an EE and my banty frizzle cochin has 9 eggs under her - one is a marans egg.
Our OEGB Blackie hatched out 6 chicks last year. She raised 5 large Barred Rocks just fine. They were bigger than she was by the time they were 8 weeks old.
My first silkie sat on four standards and three banty eggs. Three standard and one banty chick hatched. The other three eggs had not developed at all. I think they were not fertile to start with. Silkie #2 sat on 7 eggs as well, all standard size. Four hatched out. One hadn't developed at all. Two had partially developed. She sat back in January when the temps were really low AND had the four babies from the previous hatch joining her at night in the nest box, so I'm sure the eggs were not adequately covered. It was often crammed in there. Both mamas have done well with standard babies. I did notice the first hen tired of motherhood with the standard boys when they were almost her size. She allowed the banty around for a lot longer. Dunno what that means, unless size is how chickens determine maturity.
I have a small Banty Cochin Frizzle...sittin on a turkey egg! You should see her trying to balance on top of that thing. She also has 3 of her own under her.
