Looks like Avid has qualified the new Nehalem Macs:

Avid Announces Support for New Apple® Mac Pro Computers for
Avid Media Composer® and Avid Symphony™

Qualified Configurations:

Apple Mac Pro Configuration One
- Two 2.66 GHz Quad-Core Intel Xeon
- 6GB of DDR3 ECC SDRAM (6x1GB)
- 640GB 7200-rpm Serial ATA 3Gb/s
- NVIDIA GeForce GT 120 512MB
- One 18x SuperDrive

Apple Mac Pro Configuration Two
- Two 2.93 GHz Quad-Core Intel Xeon
- 6GB of DDR3 ECC SDRAM (6x1GB)
- 640GB 7200-rpm Serial ATA 3Gb/s
- NVIDIA GeForce GT 120 512MB
- One 18x SuperDrive

Notes
• Avid will not support the single Quad-Core models, or the dual Quad-Core 2.26GHz model
• Configuration testing was done with Mojo-SDI, Adrenaline, Mojo DX, and Nitris DX.
• Qualified local storage includes Avid VideoRAID® ST, VideoRAID SR, and VideoRAID RTR.