A given instance of Watson is unique based on it's corpus (documents that have been uploaded to it) and it's level of training and fine tuning. So far each instance has had to be trained from scratch, although they are making some Watson instances available that will come pre-trained in specific fields (like medicine).

The soon to come Watson platform will also come with a set of curated content. So it will be a mix of the content you provide and existing (free and paid) content.