Just a word of caution-- TIm Ackerson writes about how to feather sex and cautions about the birds from hatchery stock. He lists which breeds can be crossed to english and american breeds to have the sexlinked effects of feather sexing. His information indicated cross breeds are used to allow this type of sexing. ( see his thread).
Yes They can feather sex Their chicks, but who knows what they mixed them with to be able to do that. Those chicks have been specificly bred to be feather sexed. Does not mean that the same would be true of chicks from any other line.