Yes as others have stated already you need to check into your SVN a few config files and folders in order to make PhoneGap work when you check it out. This is what defines a PhoneGap project:
- Has a .cordova directory, with a config.json inside.
- Has a www directory, with a config.xml inside.
- Has a platforms directory.
I found that with that in place you can use PhoneGap commands without problems. If you need to see an example of those config files, just run phonegap create myapp.