Good opportunity to discuss the two different types of white found in the Cornish breed, and how they differ.
White laced red (single laced) and jubilee (double laced) are both examples of dominant white, which mainly affects only the black part of the feather, leaving red largely intact. The presence of dominant white effectively turns a dark Cornish into jubilee.
Being a dominant trait, it only requires a single copy to show itself in the colorization of the bird. One possible drawback to this is that a one copy dominant white bird will only pass the trait to 50% of its offspring. So when breeding two single copy birds together will still produce 25% dark 0 copy chicks, 50% white trimmed 1 copy chicks, and 25% white trimmed 2 copy chicks.
As fowlman01 stated, good white laced reds likely all posses 2 copies of dominant white, as there is no other single laced variety of large fowl Cornish to outcross to. Where as jubilee and dark are both double laced.
The other type of white is recessive as found in white Cornish. Being a recessive trait, it requires 2 copies to show itself. A 1 copy bird will show no outward indication that it carries it.
The other main way that recessive white differs is that it is much more effective at covering red as well as black. I have heard it described as the presence of 2 copies of recessive white acts almost like a switch, blocking pigment development. I suspect the vast majority of white Cornish large fowl are genetically dark Cornish with the pigment turned off, I know Dad's were.
Two recessive white birds (as they are 2 copy carriers) can only produce white chicks when bred together.
A 2 copy recessive white bird bred to a colored bird will produce all colored 1 copy chicks.
Two colored 1 copy birds bred together should produce 25% white 2 copy chicks, 50% colored 1 copy chicks, and 25% 0 copy chicks.