I learned what Andy said (i.e., that when they're old, sometimes dried beans of any kind will never soften) a number of years ago. Since you cannot tell how old a bag of beans is when you buy it, it can be unpredictable. So ... I've taken to almost always using canned beans, especially when I need a predictable result. It's one thing to have to toss out a dish I'm making just for hubby and me. Yet another thing to have to start all over on a dish that takes hours when you're making it for company. My turning point was when we were on the road and bought anasazi beans at a market in rural Colorado that was famous for its fresh produce --- and they never softened. Now I'm afraid that I rarely cook beans from dried any more (never say never or always) because I dislike having put 3 hours into something I have to throw away.
Yes, acid of any kind will keep them tough -- tomatoes, wine, vinegar, beer. Anything like that has to be added AFTER the beans are cooked in my experience.