It should not be found in AB. It is more commonly found in wetter, more temperate areas, such as rainforests and wet sclerophyll forests, often along the east coast of Australia. I wonder how it got there.
It's definitely not bracken, the pinnae are much broader and more softly textured. You are right though, very unusual for an urban reserve to be supporting a species like this. I'd probably put it down to being a product of the wet years.