One of the points made with Bamboo is the ability to use the CI process to control things other that the standard build stuff like backups and publishing to web sites, etc... This makes Bamboo more valuable to manage and control these other processes in a consistent way with all the metrics and notification support that Bamboo provides. However, many of those processes are schedule based and not based on repository changes. Specifically, there is no need to specify a repository at all. The request is to provide an option to specify repository of none or similar way to specify in a build plan that the repository checkout phase is not required. The build in this case is just a script.
I guess the workaround with current bamboo is configure some unimportant repository checkout