I have the following profiles in my parent pom
P1
true
Just to clarify on this, Maven Profiles are in fact inherited. For a reference to another SO question see: Inheriting Maven profiles. I have successfully inherited profiles in my project and no additional work is needed.
As for the original question, you have a variable defined in the exists element. According to the documentation:
As of Maven 2.0.9, the tags and could be interpolated. Supported variables are system properties like ${user.home} and environment variables like ${env.HOME}. Please note that properties and values defined in the POM itself are not available for interpolation here, e.g. the above example activator cannot use ${project.build.directory} but needs to hard-code the path target.
So, what I get from that is that ${project.basedir} cannot be used and will not work. If however you have it defined as an environment variable, it will work.
One caveat that I found is that in the parent pom must not be used in order for the profile-specific configuration to work.