Brett brux has been found all over the world, but I don't think that really answers your question. Species delineation in the microbio world is kind of a weird, nebulous thing. Just because two strains of B. brux are both in the same species doesn't mean that they will behave the same way, grow at the same rate, or excrete the same compounds in the same ratios as one another. Given the very quick rate at which most microorganisms important to beer divide at, evolution can progress at rates that are vastly higher than for macroscopic organisms (
for whom the definition of species can also be pretty nebulous!), so that two populations separated by a few miles and a few years can be very different from one another. As an example, look at the massive variety of yeasts that are available from places like Wyeast and whatnot. The vast majority of them are just a single species -- Saccharomyces cerevisiae -- but they are most definitely very distinct from one another.
So, in summary, yes, Brett brux has been found all over the place, but no, that doesn't mean that Lambic isn't tied to the geography.