Craig, I'd rather hear about it now than later. I think the CY leaven is still an interesting test even if it is not the original question. It would still constitute a take over scenario (i think).
I'm not saying it's not a takeover. I'm saying that a rouge yeast taking over a baker's yeast culture is not necessarily the same thing as the rogue yeast taking over a sourdough culture.
For all we know, the very mechanism by which a rogue yeast would take over a bakers yeast culture is the same mechanism by which a sourdough culture would prevent a takeover. My guess is, that if there is a takeover of the baker's yeast culture, it is because the rogue yeast comes with a rogue bacteria and together they create an environment too acidic for the bakers yeast to reproduce leaving the rogue yeast unopposed and free to consume all the oxygen and food. That same mechanism might not work in a sourdough where the yeast has already adapted to the low pH as a defense from takeover.
I think it is meaningful and can't be overstated that nature selected the yeast and bacteria in a sourdough culture and man selected the particular strain of yeast in baker's yeast. In nature, there is only one priority - survive [your competition]. That is about the last thing that man considered when perfecting baker's yeast.
In a "culture" form, do you it is too unstable or weak to maintain it's original profile?.
I donít think itís vulnerable in dry or cake form, and thatís by manís design. In a ďcultureĒ Ė something bakerís yeast was not designed for Ė it may be vulnerable. Not because it is unstable or weak per se, but because maybe it does not have any defense against such a takeover. Or, perhaps it does. Perhaps it can multiply, use oxygen, and metabolize food so much better than the competition it just dominates? I donít know. Iím guessing not, but maybe.
Personally, I think there is a fair chance that you will get a takeover or noticeable change of your bakerís yeast culture. I wouldnít put a big bet on it, but it wonít surprise me if it happens. Conversely, I do not think it is at all likely that rogue yeast can take over a healthy sourdough culture.