Which flavor of MPG are you referring to?
----- MPEG1?
As recommended above, Premiere Pro will allow you to import and edit MPEG1. Adobe makes a 30 day trial version available if you don't have it already with one of their bundles (or maybe it's time to get the Production Bundle and work After Effects and Photoshop into your workflow?)
You could also find a utility that demultiplexes MPEG1; however, you'd probably want to convert it to Photo-JPEG at something close to 320x240 in frame size. You'll have to create a custom Easy Setup and/or Sequence setting. You could start with OfflineRT NTSC and change the compression amount from 35% to 100%.
If you're not going the Premiere route, search Google for "How To Demux/transcode/convert Mpg on Mac" and some options will come back.
Also, if you have Roxio Toast, it might be able to do the conversion for you.
But, with all that said, the only time I use Premiere Pro is when I have to cut MPEG1.
MPEG1 is meant for viewing video on a computer and/or devices that support MPEG1 at "VHS" quality. Or, simply put, this is almost the worst possible source video you could be given. (I'd put Photo-JPEG video streams from early point and shoot still cameras just below it. But then again, those would be easier to try to edit at first only to have the picture completely break apart when you try to export it). Two decades ago, MPEG1 was awesome, but even then you encoded it from an edited master that was on something better than VHS.
If you can find some hardware that will play MPEG1 out via S-Video, it's probably worth patching that to a DV media converter or DV camcorder and pass that through to FCP at DV-NTSC settings.
----- MPEG2?
The MPEG2 QuickTime component should already be installed via Final Cut Studio, allowing you to open MPEG2 streams directly into FCP; however, you'll probably be better off batch converting from MPEG2 to DV-NTSC and then cutting at the DV-NTSC easy setup.
----- HDV (MPEG2 codec for picture and MPEG1 Layer 2 codec for sound)?
I'd guess this isn't the type of MPEG you're talking about based on your post. Also, this is, of course, supported in both versions of the studio that you have.
-Warren