This is what ive understood so far reading the code of the events leading to the burgundian crisis:
1.Burgundy strarts with a modifier called Burgundian crisis making almlsost impossible for burgundy ruler to concieve a new heir and this is meaant to last untill 1500 or if the burgundian crisis is resolved(the curremt ruler gets -100% chance of getting a new heir and also disable the option for introducing new heir). The only way for burgundy to get a new heir with this modifier is if the current ruler is not married and get the event that marries him and also gives him an heir.
2.In the meantime there is an event that gives a female heir to burgundy if the current ruler doesnt have an heir; that is meant to happen in 120 months strating in 1457. That female heir is Marie de Bourgogne and she cannot be uninherited while the crisis modifier is active.
3.When the current male ruler dies and Marie gets the throne then the Burgundian succession crisis event fires and she gets those 3 options that we saw in the dev diaries, with the emperor enforcing HRE lands if the one who get the inheritance is not himself. (I think that this can also happen if the current ruler dies heirles, because in one of my games France got a PU over Burgundy without a RM when Phillip died heirless). Im not sure what are the modifiers for IA Burgundy to decide the outcome but i think it has to do with of course having a RM, good diplo relations and high development (the country with more dev having a RM with Bur is most likelly to get it).
4.Then there is another event that gives you all of burgundy lands for free if you have a PU over them via this event.
