I found in Vegas 8 (not DVDA):
Tools->Burn Disc-> Blu Ray Disc Then you have the choices of:
-render Image & Burn BD
-Render Image only
-Burn existing image
and choice for Compression, including MP4 etc.
I actually burned a 1.5 hour BR image (18 GB). Getting my Sony burner today. Let you know what happens.
JK