Mine live together fine, when the turkeys are young the Muscovys are boss, then the turkeys take over.
I've seen the turkeys give the ducks the odd peck on the head if they get too close but apart from that nothing.
fast moving Muscovy ducklings however seem to scare the life out of turkeys!
i've often seen a duckling set off running and stampede a fully grown group of them!
Must be like the mouse and the elephant thing