I find that one hard to believe - I can't believe Bill would open himself up to cartel laws, the others however :-) Though that would explain a few things
Bill and Steve would meet in a plane flying over the ocean - in order to prevent anyone else being involved and to prevent any monitoring. And, in general, these deals made them very rich, so the only people who could betray them had both made a lot of money and been involved in illegal activities themselves. Kind of hard to see much risk in something that is completely deniable. If I hadn't spoken to people with direct knowledge of these things, I wouldn't know it myself. I'm not sure what it would take to get people to admit to their involvement.