This painting has more of an illusion of depth and color than might seem possible using black and white because there is in fact a difference in color between the grays made with the black used transparently, and the grays made with black and white. The grays made with black alone are warmer, and act as shadows. The grays made with a very small amount of transparent white act as midtones. The grays made with the stronger whites act as highlights. There was no pure white used in the painting.
This is a simplified and abstracted example of one aspect of how older paintings were made which has become somewhat lost. The most important aspect of this system when working with color is not the local color - the "red" roof, the "green" grass - but working from the light-shadow axis of the day, setting up whether a given value is a shadow, a midtone, or a highlight. The corresponding paint then being transparent, translucent, or more opaque, which adds an element of color even while using black and white. This might be called painting from the envelope, because it begins by establishing the light-shadow envelope of the day. Once this envelope is established, local colors can be dropped into it without the laborious "hunt and peck" method of making each color correctly from scratch. This technique allowed older painters to maximize the sense of visual depth in the picture plane while using a palette composed of simple and reliable earth colors.