No, it is not used because you can have AFAIK use only one view handler.
But it should not be too difficult to write a *.taglib.xml.
It's definitly possible to have both jsp and facelets pages in a single app.
That came handy for me when migrating a large app.
See for example
But Felix is right, you would probably be better of just writing a taglib.xml - and of course complain at ILOG.