Nicolas told me that the actual order for static dependencies in that  
example would also be that one :

> (((B1 || B2); B) || ((C1 || C2); C)); A

However he points out that there's still a difference between static  
and dynamic dependencies : static dependencies can control the way  
rules are selected. If two rules can build a target but the first rule  
has a static dependency that cannot be built then the second rule will  
be tried. Dynamic dependencies cannot do that since once a rule is  
invoked it is considered to be definitively selected.

Best,

Daniel