Yes, ornamental plaster can be repaired, however it is time consuming, utilizes special materials and is best left to a professional's touch. In some cases, molds must be constructed to "cast" the shapes due to their intricate detail.
For some profiles, a template can be constructed to provide a continuous pattern. In others cases, the shape must be recreated by hand tools and the knowledge of a professional. We have these repairs and would be happy to take a look at your project.