Maybe they're betting on the British pound to drop so they can hire engineers on the cheap. My understanding is that salaries (for software developers) in London are already pretty low compared to the US and even Canada.
https://www.google.com/search?q=google+eu+fines&ie=utf-8&oe=...
I can assure you that if it was up to me they'd either pay or get blocked. I really don't understand this mentally whereby companies avoiding taxes is Ok. Who do you think pays the taxes that they don't?