We wouldn't recommend it, but it is possible. Even set to 250W any 600W dimmable ballast will send enough current through initially to power up a 600W bulb. As the 250W lamp isn't designed for this its life span is significantly shortened.
We don't sell 150W Ballasts so we can't say for certain but we don't believe you'd be able to power 150W CMH with a 150W magnetic ballast because of their higher frequency.