Could I work as a Professor in Europe if I only speak English? My wife is finishing her doctorate in a few years in a very specific field: Assessment (or Language Testing) of learners' English as a Foreign Language. She will probably apply for research professorships (including advising doctoral graduate students) when she graduates and I have suggested that she try to broaden her horizons and look for positions in Europe as well as in North America. She is nervous in part because she only speaks English (and Mandarin Chinese, which I imagine wouldn't be too helpful).

Are there professors in Europe who don't speak the local native language? Are there areas or universities in particular where people working in academia can get by while only speaking English? Any personal experiences would be greatly appreciated.
You can certainly do with just English in most countries. 
This is true even for countries like Spain or Italy where English is not that widespread.
Personally, I've worked on a few Spanish universities and some of my colleagues didn't know any Spanish at all when they first arrived.