I was going to say no, but now that I think of it, it may be possible to use calibre-provided metadata (with custom columns, templates and everything) in the custom CSS. I'll have to play a bit with it and implement it, but my idea currently is something like this in your CSS:
Code:
body {
string-set: booktitle @{title}@
}
where @{title}@ would be converted into "Book Title" by calibre before passing the CSS to Prince. I'll have to think about the syntax too.