Yes, I can confirm that the Eurofighter Typhoon can operate with NATO forces. Italy and the U.K. are part of NATO, and all their assets have thorough NATO interoperable capabilities. The air forces of Italy and the United Kingdom have chosen to operate the Eurofighter Typhoon in the air-to-air role. That would leave the air-to-surface role to the JSF, to the F-35. For this reason, I'm pretty sure that the Eurofighter Typhoon will meet the NATO interoperability requirement. It's up to F-35 to show that they will meet the NATO interoperability requirement with the Eurofighter Typhoon, as this aircraft will be in service in two of the air forces of the NATO alliance.
On December 7th, 2010. See this statement in context.