cataloguing/addbiblio.pl has a routine BiblioAddAuthorities which is almost identical to the subroutine of that name imported from Search. Name clash should be resolved. If code exists in two places at least one is bound to be wrong
Furthermore, the core routine BiblioAddAuthorities should not be in C4::Search. C4::Biblio, C4::AuthoritiesMarc, or perhaps a new module would be better.
This will be fixed as a side effect of the work on bug 7284.
As stated in comment 2, this was fixed by bug 7284.