I'm pretty sure they will. EU has pretty good lawyers as well.They won't Google will pay 2.4B to a legal team before they do that
Remember the environment here is very different to US.
Companies rarely win cases against the state. Tax legislation is very precise (we can easily say: way too complex).
Also I doubt this would be a good PR move for Google.
If they'd won such a case against a government agency in US, Americans would celebrate. A private company (just how many times did you mention that?) beats the state. They keep the money they made - that how it should be!
In a similar situation in Europe they would be widely criticized by media and citizens. Yes! The people would take the side of the state.
IMO it's not worth it. They might lower the fine during negotiations, but will have to pay eventually. The actual issue here is: what to do next? Will they change how Google Search works? (doubtful) Will they put a huge banner on top saying "we're promoting our products"?
And whenever you think that EU regulations are stupid and US-based companies will simply ignore it, just think about the Cookie Law.