Absolutely! I think the first one I made, now that you mention it, was made with cultured buttermilk. I am pretty sure I have seen Jeff use buttermilk often.
The way to "prepare" your buttermilk culture is to buy a good quality cultured buttermilk, set some aside in a container (I just use a glass jar ... the type used for canning veggies) and add some 2% milk to it and let it sit out at room temp for 12-16 hours or so. Then, pour some out and add more 2% and repeat. After 2 or 3 cycles you have a jar full of very active buttermilk culture. You should notice that the mix will thicken up faster as you cycle. Maybe 12-16 hours first time, and then 8-12 hours 2nd or 3rd time. If you see 8 hours you are probably good to go.