As a user of Perforce, I don't want Bamboo to ever "clean" the build area.
All it does is mess up the environment. It might work if it understood it needed to do a force sync after deleting all the files (p4 sync -f ). There was an option saying "don't manage my workspace" and I have always selected it. But Bamboo does not respect it. For me this is critical and it is a bug.

For instance, if I move the plans to a new server, I will change the name of the workspace. Bamboo will delete all the files, the build will fail. I have to go on the server, do a force sync, re-run the bootstrapping process for our application, re-run the build.

There is no way to do this cleanly.