Its a yeast eat yeast world out their Oliver. I think Coopers did it so they could get larger brewing conditions (speculating on my part)
Spontaneously ferment? Sounds a bit like Divine Intervention.
All bets are off when a Deity becomes involved
Chances are those yeasts have pretty compatable conditions, I was actually refering to a Lager vs an Ale.
If you pitch one of each, the one that has the best conditions will preveil. For example, I have a Coopers Lager and a Coopers SAF Lager. I pitch them at 75 deg F, which do you think will blow the lid off the fermentor?
I have Coopers Ales which are done and dusted in two days. I have Lagers which are just getting going after two days. So that little old lager had a snowballs chance of adding anything to the beer.
That being said if you could find a yeastie that is happy to chew on malto-dextrins then it will impart some of its charecter into the beer, although you would be pissed at it as you would have no head retention but hey, thats another issue.
Dogger