Pulumi doesn’t know about them. The deployment works as any other ARM template would: if you do it in Incremental mode, it won’t delete old resources. In complete mode, it would delete all other resources in the same resource group (which is probably not what want).
OK thanks. The template deployment is only a small part of the bigger deployment. Most of the artefacts are deployed using normal Pulumi code. The template deployments are just for the bits that don't work the standard way. Everything is going in to the same resource group so I can't use "complete" mode