Anyone had experience migrating inwards to GW ?

I have a subsidiary site that uses MS Small Business Server 2011 with Exchange and it is a dog. I can place their emails in the cloud but an option is to bring them into my GW 2014R2 deployment if I can find an easy way to migrate.

Any suggestions for GW2014 ? I've seen solutions for GW 7 or so, but nothing since. Are there still tools around ?

Thanks