Can I eat cheese which has been "infected" with blue cheese mold? Recently, I bought two pieces of cheese - St. Agur and Pyrenean cheese. They were cut from wheels, not pre-packaged. At home, I removed the foil and placed them in the same plastic container in the fridge. 

Two days later, the Pyrenean cheese had some mold with bluish tinge on the surface. I assume the seller has stored the cheese properly, so it shouldn't have gone moldy by itself in the short time in my fridge. I think that the benign mold from the blue cheese colonized the Pyrenean cheese. Still, I decided not to risk eating it (I still ate the blue cheese). 

Is this what really happened? If it happens again, can I assume that it is edible mold? Is it safe to eat edible mold after it has colonized another type of cheese, or will the changed food prompt it to produce dangerous byproducts? 

Also, could I have prevented it by having the cheeses individually wrapped in foil inside the same container, or would only keeping in different containers stop mold propagation?
Well, first off, mold grows from spores, and your Pyrenean cheese was likely already "contaminated" with Penicillium roqueforti, Penicillium glaucum, and Penicillium candidum spores at the cheese shop (it'd be surprising if the cheese shop isn't covered with them!). So, if you keep it in a environment habitable to them, they will grow. I suspect that you'd get the same results even if you put them in two different plastic containers.

As to its safety, if it was indeed one of the used-in-food Penicillium molds, it should be safe to eat—you can make sheep's milk blue cheeses (e.g., roquefort) after all. But the problem is that the same humid environment that encouraged the Penicillium colonization also encourage other molds—many of which you don't want to eat. Also, I'm pretty sure there are blue-green molds you don't want to eat.