What a good question! I don't know for sure, but as Nickel Silver is an alloy consisting of Copper, Nickel and Zinc in solution together I'll stock my neck out and guess!
When a Nickel Silver anode is electrolysed, I think the current will remove atoms preferentially in order of their position in the electro-chemical series. Zinc will be removed first, leaving a spongy mass of Copper and Nickel, then the Nickel will go, leaving a spongy mass of Copper, and only then the copper will transfer.
So I predict the cathode will be plated with a layer of Zinc, then a later of Nickel, and finally a layer of Copper. The layers will be imperfectly pure, but the result won't be Nickel Silver plating.
Dave