Can XDCAM EX footage be imported and edited with Imovie09?

Yes, use Sony's file transfer software to bring clips into movie folder.

If you have Final Cut Pro (which includes EX codec) then it'll import into iMovie.
It's possible that CalibratedSoftware's codec for EX MP4 or EX MOV might do it without FCP on the system.

Otherwise you'll have to use XDCAM Transfer to downconvert to .DV.

I'm thinking if there's a way to convert to AIC (Apple Intermediate Codec) you'd be able to import and keep it HD.

Thank you.