If you are keen to shoot video on your iPhone, but you cant access your files, then you can copy the films across to your computer with iFunbox. This program allows you to explore your iPhone as you would any other device, through a folder hierarchy, so you can access those move files.
It is available for Windows and Mac, and its also free! get it here.
note: Videos shot on iPhone 4 will be 1920 x 1080 (HD resolution) but compressed with H264. They may need re-compressing to HDV in order to be edited in Final Cut Pro. The tool for this is MPEG Streamclip, which will allow you to re-export your film as a HDV file.