I wouldn't keep the meatbirds and laying hens together, as they should have different feeds (meat birds, ours get a mix of wheat and grower pellets, and the layers get layers pellets, different amounts of protein in the feed), also I find that the meatbirds scoff ALL of their pellets wihtin about 20 minutes, then sit all day and look out for me just in case I bring more, no way do they take exercise of any kind...
Also I have a cockerel in with my layers, wouldn't want him to try and injure himself on the not-so-slim meatbirds (ours are just coming up to killing, so they are big). The meatbirds have a few cockerels in there, not sure what the dominant layers cockerel (a Maran) would do to the bigger, but immature meat cockerels... they are just trying to crow, but it's at the really funny sounding stage..
So, yes, I would keep them separate...