Different sorting schemes in different sections of bibliography

This is not currently possible. However the functionality for this is implemented in biber already and will be made visible through biblatex in the near future. This will allow you to specify different sorting not only for each refsection but for multiple bibliography lists in the same refsection.

This is now possible with biblatex 3.x and biber 2.x:

\newrefcontext[sorting=nty]
\printbibliography[type=book]

\newrefcontext[sorting=ynt]
\printbibliography[type=proceedings]

In older versions (biblatex 2.x and biber 1.x):

\printbibliography[sorting=nty, type=book]

\printbibliography[sorting=ynt, type=proceedings]

Biblatex 3.0 (2015-04-20) introduces the concept of bibliography contexts for this. See section 3.6.11 of the manual. (For this reason the sorting option in \printbibliography has now been deprecated.)