There are spec sheets from the manufacturer that tell you exactly what you want to know. Unfortunately, I don't know how to get access to them. I've seen the Danisco ones (I think there might be a link in the "Library" section of this forum -- just from memory).
These buttermilk cultures can indeed be quite different. I have discovered, though, that it is relatively easy to culture them from existing cheese (contrary to common wisdom). If you have access to similar cheeses to what you are making, I'd recommend giving it a try. Just follow basic sanitation steps. Mash up about 20g of cheese in some milk and then mix it with another 500 ml. Leave it at about 25 C for 15-30 hours, or until it gels. I use new UHT milk for this because it gels better (and is free of bacteria). Then take about 20g of that yogurt and do it again. It should go much faster the second time. Depending on performance, you might want to do it one more time. At this point it's pretty stable.
I usually try to watch it closely *just* as it's gelling (so keep an eye on it every hour or so when you get to around 12-15 hours in). As soon as it gels, I stick it in the fridge to slow it down, or reculture it right away. This keeps the pH relatively high (up around 5.0, I think). I find that helps maintain a good balance of the main bacteria, since some like it more acidic and some like it less. This models the whey cultures fairly closely for these cheeses, as well.
If you have a pH meter, you can make a graph of the pH over time, once you have a stable culture. You can also sample the flavour of the yogurt. The main thing you'll be missing are the enzymes that develop flavour as it ages. However, you should have some idea of that from the cheese you originally bought.
BTW, as far as I can tell, this technique of reculturing bacteria from cheese seems to work for basically all cheese that isn't heat processed (i.e. mozzarella would obviously not work). Even long aged cheese seems to work. My dad has had a lot of success with cheeses like Emmental (though no proprioni shermanii, it seems).