I notice that these people do an ign for 90deg TRi, BSA, and Norton; http://www.pazon.com/pages/home.asp?s=ZQZIA2hVZlBy
Its doesn't appear independant for each cyl though, so like a lot of Ducati aftermarket igns, there would be some odd angle idle sparks. Which a single fire if I'm interpreting the discription properly won't have. THen again if it has a pickup rotor with 2 triggering gaps I don't see how it can be single fire. Which you can get with 1 trigger rotating past 2 independant triggers to 2 independant igns, if they have 180deg gaps and 2 triggs-2igns, maybe they are also producing an idle spark near tdc only, and you don't get your cyl angle moving the gaps but the triggers they trigger.