I've seen a handful of recipes recently using frozen prepared hash browns in casseroles and crock pot dishes. Can you directly substitute shredded or small-dice fresh potato, or do you need to adjust time or water or anything else? I like the idea of making breakfast casserole, and i'd like to avoid having mashed potato in it.
If the recipe called for hashed browns, I'd probably brown the potatoes a little before tossing them in. In a crock pot, the cut up or shredded potato would probably disintegrate.
If you want the potatoes to hold their shape a bit, browning would do it.
Read a bit on the "Cooking Light" site. They try to specialize in lightening up the fat and total calorie content of recipes with sacrificing the taste. In this case, browning the potatoes by lightly spraying oil on them and baking them until browned would keep you from loading too many extra calories.