Yes, I have come across them before. S&T Poultry do them, just googled them and recall seeing them on their website. I'm guessing that it was developed by Sasso. Being French, I imagine it's going to be pretty good.
My La Bresse venture is going a bit slower than I would have liked as I've been really ill the last few months but I've got some things going. I've recently put 20 in an incubator and another 10 under 2 broody bantams. Just bought an 80 egg incubator so going to start collecting for that soon. Turning a shipping container into a brooder at the moment and then need to drag my old chicken tractor out of the woods. It's been sat there about 20 years, I used to use it for my OEG bantams. It's quite big and will be used to pasture the fowl until they are big enough not to be taken by the red kites.
They are indeed amazing layers, lovely cream - flesh coloured eggs. Both my bloodlines seem to lay later on in the day. I haven't had any go broody yet. Beautiful looking birds with the big red comb, white feathers, blue legs and the exaggerated chest of the cock.
Do you dispatch and dress the birds yourself?