In bullet 3 of paragraph 4 of 12.2.4.3 [over.ics.rank] are two sub-bullets dealing with overload tiebreakers:
binding of an expression of type C to a reference of type B& is better than binding an expression of type C to a reference of type A&,
...
binding of an expression of type B to a reference of type A& is better than binding an expression of type C to a reference of type A&,
Presumably both of these tiebreakers should apply to rvalue references as well as lvalue references.