i use them in addition to fresh or frozen blueberries in muffins, and they don't require any rehydrating for something like that. in fact, they hold up really well in cookies & quickbreads.
when i make my very berry granola, i soak them in a mixture of pomegranate juice & hot water before folding them in so that they don't dry out too much during the baking process and end up with the texture of shoe leather.
in terms of pies, cobblers, etc., i'm inclined to disagree with lupaglupa [sorry!]. due to the texture & moisture of the dried ones, they aren't appropriate as the sole source of fruit in a filling. but if you use them in combination with fresh or frozen ones, they'll be an excellent addition. every year for thanksgiving i make an apple tart with dried cherries, and it always gets rave reviews. everyone seems to love the unexpected addition of those little cherry nuggets.
I use them as is. They aren't all that dry - not leathery like craisins or raisins. They work well in scones and other recipes where fresh blueberries are just too mushy. I don't know how they would work in a pie, say, but my guess is they would be fine without hydration - simply less watery than fresh so no thickeners would be needed. And they are more sweet so you will want to cut the sugar back a bit.
I'd have more experience to tell you about if they weren't so darned expensive!
You could try rehydrating them in something like brandy! Usually use them in a compote, so basically they do become rehydrated while they simmer with other ingredients. I would heat the liquid and let sit overnight. They will have way more flavour than fresh but I don't think you will ever get them to the texture of fresh. They might be like 'raisins' in your recipe. Experiment!