I know that in beverages soy is a great substitute for milk, but what about in baking? I did try making french toast one day. Instead of putting milk in with the egg I put soy. It seemed to work alright but that's still not baking.
Yes, you can sub soy for real milk in baking - 1:1 replacement ratio. Now, depending on the recipe, there will be some changes. For example, in bread that used milk and doesn't have any additional fat or sugars - the bread will not be as tender and will stale faster, the fat acts as a tenderizer and a moisture retainer, she sugar attracts moisture from the air to help keep it moist.
Soy also can cause things to brown more than milk.