The answer seems to be a big NO, at least not without doing some kind of plugin.
This is an issue raised alot on the ExtJs forums as well, citing the same issue I have which is that you don't always know what text is going to be used for the Label. i.e. Internationalization.
Here is one post that looks interesting: http://extjs.com/forum/showthread.php?t=25758
I don't suppose anyone has already done this???