If this is the result of Taphrina cerasi then presumably not good for anything.

prunus serotina ???

ken

Propably not prunus serotina, but rather some european species. Doesn't really look like prunus avium though.

Taphrina occurs on P. avium and P. cerasus. Low forking implies P. cerasus, but P. avium is still possible.

I think it is a regular cultivar of a cherry tree without pruning. I see some signs of human activity...so it might be a left fruit tree like the ohers on the picture. If I know well mostly cherry trees are grafted to P. avium in Mid EU. I use it for understock,too. It grows like weed around.
I would like to see, if it has cherries on that mini shrub ... :)

Is this W.B. agent lethal to other cherry trees?

From link below, however I don't understand if the broom growth flowers?

Witches Broom
The causal organism: Taphrina cerasi.

Disease symptoms:

This fungus cause's large number of irregular small branches this fungus causes large numbers

To develop on twigs and larger branches forming a witches broom. Blossoms develop and the normal branches.

Large numbers of broom may eventually kill a tree.

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Otherwise, it looks very interesting to have a shrub form and highly desirable for grafting.

Dax

Here is a link that might be useful: Shoura Group Cherry Diseases