Transferring to Europe - Language Requirements?

Hey all,

Bit of a crazy question here but here me out. I'm starting as a Senior Consultant (post-MBA) at a T2 firm here in Canada come the summer, and have a question for you. The firm runs on a regional staffing model; NA, EU, MEA, Asia/Oceania. My French is fine (conversational, lived in Montreal, etc) but not fluent or fully confident in working in it at all times. However, my partner got a job in Europe and am looking to transfer to one of our European offices sometime sooner than later. I know each region has their own P&L, you have to get buy-in from some of the partners to bring you over, etc. and what comes with that request.

My question is, when it comes to a company with a regional staffing model, how important is it to be completely fluent in the country you're trying to transfer to, if all of your teams operate in English? Would totally make sense if you need fluency for both to maintain office relationships, have a more local tinge to each engagement, etc. but am curious on this front.

Cheers