And an even easier work-around is to write the font selection into the
*.bib file directly:
title = {{\arial उद्दिष्टः समाहितचित्तस्य योगः । कथं व्युत्थितचित्तोऽपि}},
Ok, I think that will work for the few works I have to cite in
Devanagari. Now I wouldn't get into the actual macros of BibTeX
anymore.
S.