As far as I know, the HRE will always sell Bologna (at least in the early game, where keeping it doesn't seem to be in their interests - understandably so, because I've never seen them hold on to it for longer than 10-15 turns), as long as the price is right. Some people have gotten it for something like 500/turn for 10 turns, but for me it always cost over 10,000 florins. However, in all my games, they've ended up selling to me, even if I was at war with them.