Interesting, I didn't realize they're considered nuisance trees, but then then in this area of so few trees, any tree is sacrosanct.
They're commonly grown in my area, as they're drought-resistant and establish in almost any kind of soil. However, they never seem to bear fruit in this area, so perhaps that's why they don't spread on their own.
I've never seen Russian Olive trees that weren't purposely planted, mostly as windbreaks. My uncle planted several in his orchard, but after 20 some years has yet to see a single fruit, although the trees themselves are thriving.