Did the company suggest that you could contribute to its 401k? While working in Europe, will you be an employee of the company's US operations?
As an example: I transferred for my company from the US to its European operations. For all intents and purposes, I quit the US company, and was hired by the European company. I participate in the Irish company pension plan. The US 401k, in which I still have money, is not an option for further contribution.
Unless you are considering some kind of ex-pat / international service assignment, where some or all of you pay still comes from the US, I don't think you will have the 401k as an option, either.