tiny fonts for IEEEtran not working on biblography

That is deliberately prevented. You must understand that the IEEEtran class really works as a sort of 'container' for the contents of your paper and effort has been made to have all the formatting already done, so all the papers in the journal/conference proceeding will look the same. So it's not a good idea to alter the formatting, unless you know, what you're doing. But enough of this sermon, of course there is a way around it. :) You should try to modify the font size in the preamble, like this:

\renewcommand{\bibfont}{\tiny}