I agree with Galen here, the use of canes doesn't seem likely to me. How about this:
CAC is famous for colors that do not mix or bleed. One of the most interesting things about this cullet is that it is not a homogenous mixture. It was obviously molten, or at least partly so, and yet the different colors of glass remained separate.
Guineas are, essentially, veneered marbles. Could they have put a mixture of differently-colored small glass beads or bits, made seperately in batches and processed to a fairly uniform size, into the "veneer pot" and then applied that molten heterogenous mixture over a base glass?
I'm not smart enough to know how they may have actually done this but, in principle, it seems pretty strainght forward. Am I crazy?