It pulls itself along the cables rather than using a propeller, yes, but the motor that's doing the pulling is on the ferry rather than on the shore. To answer

It pulls itself along the cables rather than using a propeller, yes, but the motor that's doing the pulling is on the ferry rather than on the shore. To answer GP's question: I don't know, but given that this was a retrofit of an existing diesel-powered ferry I could guess that this was the cheaper way of doing it.