This gives a (slightly) more conventional view, involving annihilating positrons produced from primordial black hole Hawking radiation, these would aniilhilate with the electrons in the radiation.
Milky Way's antimatter linked to exotic black holes - space - 22 January 2008 - New Scientist
Some discussion is here of failures of direct primordial black hole radiation detection-
Fermi: FAQ - "Mini" Black Hole Detection