When a crate awards superior regional items, you have an equal chance to receive any of the superior regional items currently available to you. So for example, if you have 4 toon types unlocked (Forest, WB Studio, Avalooney, Town) and you get a superior regional item from a crate, you have a 25% chance of it being a hydrant. If you have unlocked all the areas in the game (9 currently), then your chances of getting a hydrant are now 11.1%.