While I was not at the time trying to do it via Profile Manager I did previously look at trying to enable Location Services via a script. Unfortunately I found it too hard or more accurately I failed to do this. I ended up 'cheating' by logging in on a test Mac, manually setting up Locations Services the way I wanted including most importantly setting the Security & Privacy settings to allow a specific application to use Location Services. I then saved a copy of the relevant configuration file which is -
/private/var/db/locationd/clients.plist
I then as part of my DeployStudio workflow to image fresh computers included a step to copy this to the correct location on the fresh computer, thereby 'restoring' the settings.
So the short answer is that /private/var/db/locationd/clients.plist is the file but the structure is such that a simple defaults write is not possible.
Let me know if you get anywhere with this.