Actually, this makes sense.
Vodafone its the only operator who could provide "almost" global coverage in Europe, this would mean Amazon only has to negotiate and sign one deal.
To my knowledge no other operator is in this position in Europe.
(Not to mention that operator fragmentation would complicate manufacturing and distribution.)
So at the very least the rumor has some credibility.
I'm also thinking that in Europe Amazon could even have the final customer buy (or use) a SIM and pay for bandwidth.
Although that is unlikely, it could be the easiest way for them to expand.
If Amazon is really moving that fast, it would also mean that it has secured global distribution rights for kindle titles.
Good news indeed.