[gregdunn]

>I'm forced to wonder whether the same strain of yeast also survived on the surface near the original brewery location

Maybe something similar to it. Commercial breweries were selective in reusing batches of yeast even back then. House strains were refined over time to reuse batches that had fermented the most reliably, produced the fewest off flavors, etc. The yeast they used might also not have been local in origin.

But the wild ancestor might still be around, somewhere. (It's also possible the yeast they have is a wild yeast contaminate, as noted in one of my other comments in here)