I'm making a blueberry buckle pie and it calls for a spring form pan.

Although I think the question has been answered, for anyone interested in why we do what we do in the kitchen:

Cheesecake = custard, buckle = cake.

The purpose of a water bath is to provide gentle heat, important for custards which are more tender when cooked slowly. The water regulates the higher oven heat, holding it down to no more than 212F (but typically even lower due to evaporative cooling).

Cakes require higher temperatures to initiate both caramelization and Maillard browning. The Maillard reaction doesn't begin until above the boiling point and sucrose (table sugar) browns still higher, around 330F.

I am guessing that the springform pan is used simply to help you remove the pie from the pan for serving purposes. Springform pans are great for baking deep dish pies or coffee cakes, since you don't have to invert the pan (and have lattice crust shatter or streusel topping rain everywhere) to remove the finished product, and can serve pieces from something other than the pan (which can keep hungry people from using your nice knives to cut in your nice pans).

Yes, a springform will let water in; but, you could line it with aluminum foil (buttered) so you can easily get the buckle out of the container.

All of the above correct. I would use a springform pan for a buckle or a crumb cake to crisp and brown the sides--to keep the crumbs inside the cake! Definitely don't use a water bath, as this will negate all that beautiful crisping.

If you are trying to make a Buckle, a waterbath will only make it soggy and sad. Bain Marie, or water bath is keep the cooking environment humid. Buckle will benefit from a dry cooking environment so you can get the quick bread crisp.

No. A waterbath is great for cheesecakes and custard-like desserts that would benefit from even heating (which the water provides). I think you associate the springform with a waterbath because most often, it's a cheesecake recipe.

I don't think so.