You might try installing Perian (
http://www.perian.org/) if you don't have it. Amongst it's supported files are MS-MPEG-4 v1 & v2, and MP4S is Microsoft MPEG-4. Once that's installed you'll hopefully be able open the files in QuickTime Player, and export them to other formats. If it really was 1080p at some point, what you have now is either going to be letterboxed 16:9 in 4:3, or anamorphic 16:9 squished into 4:3. You could export that to DV Stream, DVCPRO50, PAL, Progressive, and with some amount of luck take that into a 25p FCP document. It's pretty certain that what you have is SD.
The editing possibilities are better if it is MPEG-4 than if it was MPEG-2. If you can open it by having Perian installed, you should be able to do initial editing in QuickTime Player.