I do not know: I consider the plums in Kansas to be a bit thin, and then they lose their leaves in the winter. Pinching the young trees should make them bushy, but there is still the part about them losing leaves in the winter.
There are several plum cultivars that work here .. I'm wondering how they'd suit the privacy component though?
Amongst the Caragana family is one species, arborescens, known as Siberian Pea Tree. It is native to Manchuria and Siberia, so it would feel at home in zone 3.
Deer love it for browse, and the trimmings make a good fuel wood. In Siberia, the green pods are used as a vegetable, and the dried beans are often used as chicken feed, as they contain 36% protein. The bark has been used for rope making.