Does MettleCI use the IBM Connector Migration Tool?

When used for Rapid DataStage Upgrade, yes. MettleCI's deployment plans can automate the invocation of the CCMigration tool to upgrade old Enterprise stages to the new Connector stages, among other changes that CCMigration tool is configured to implement.  The build plan will also record all changes made by the CCMigration tool.

Additionally, MettleCI provides a job transformation capability called Transmuters.