XML & sharing namespace nodes

The Scala XML book
(http://burak.emir.googlepages.com/scalaxbook.docbk.html) says:

The current implementation will not properly stratify namespace
bindings when elements from different scopes are combined. This is
not a problem when querying or processing XML data, but it might
lead to wrong namespace bindings when serializing XML. A modified
version of the serializing algorithm can solve the problem by
introducing namespace declarations and undeclarations in the right
place. Since it seems a rare problem and developers can stratify
namespaces themselves in a given XML application, your humble author
and scala.xml maintainer did not consider this issue a priority.

Can anyone shed any light on how best to go about this? In a nutshell I
need to insert an Elem deep inside another Elem, and have its namespaces
bubble up to the top. Probably not that hard ... just wondering if it's
been solved.

Thanks,
Eric