Firefox does not wrap words in
<a title="longword" style="word-wrap:break-word;"></a>
No, you cannot make Firefox deviate from its way of rendering
title attribute values; cf. to How can I use a carriage return in a HTML tooltip?
The tooltips created by using
title attributes are of questionable usability (tiny font that cannot be easily increased by the user; disapperance after some seconds; etc.), so they are suitable (at most) for short advisory titles (mainly for links), which not cause a need for wrapping.
For longer tooltips, consider using CSS techniques. Or just put the tip into the text proper.