Figures if two B units have smokers in an ABBA set, in addition to both A units with smokers - that's 4 elements on one transformer - not to mention probably at least 4 motors and sound boards too... I don't think even an industry standard old ZW will handle that kind of torture for very long, so I can understand if this is the reason for cutting corners.
But I also have no idea if the real B units sourced power from the A unit(s) or if they actually had smoke exhausts too... Any experts who know the answer - it would be great to hear from you.