This question prompted when I was answering an Engagement Plans question. I couldn't find an answer anywhere nor an explicit mention that Marketing Automation Plans are essentially replacing Engagement Plans including in Sitecore Docs. Anyway, does anyone know if there's a tool for this type of migration?
Due to the technological and fundamental differences between Engagement Plans and Marketing Automation, there is no migration path short of manually recreating the plans.
Marketing Automation uses different workflow logic and it's integration with EXM (in 9.0.1+) are much easier to use and more clear.
Lastly, because of the Silverlight implementation of Engagement Plans, a migration path is not possible.