It seems to me that the bacteria don't just kill bacteria- as far as I understand it, they share that duty with your curing salt (in this case #2, right?). For us, who have fridges, in the modern world, the most important thing they bring besides another measure of safety is that they completely change the taste of the meat! They are a mix of bacteria that is much like the bacteria used to make yogurt, and some cheeses. I know that the stuff from BP includes at least one strain from Lactobacillus, which is the same genus as you find in most yogurt. Yogurt sure does taste different from milk, and the low pH allows it to be more stable. At the same time, just like your body, or yogurt, you want your sausage to be colonized by benign bacteria, not nasty kinds! That, in addition to the low pH will reduce the risk of later infection by the unhealthy ones!
By the way, I just made my first bacon- cherry smoked with brown sugar in the cure, and it smells AMAZING- I fried up a few thick chunks and diced them into a potato salad with mayo, green onions, green beans, and salt and pepper. Served it warm. Mmmmmmmm.
This, then, brings up a question I've had for a while. If the drying is being done in an environment below 40 degrees, is it necessary to use bacteria (Bactoferm) at all? In other words, is there any threat of botulism if the sausages spend their entire drying time within the so-called "safe" temperature range? Any thoughts?