I tried searching for this but didn't see anything definite. I'm curious as to what bit rate VP uses when you choose the 'Burn DVD' icon on the toolbar, using VP 12 or 13.
This the result I got from a DVD I just burned from the Vegas Pro 13 timeline. Looks as if the target bit rate is ~8 Mbps.
NOTE:
Burning a Blu-ray from the timeline allows you to use custom templates that you build to suit your preferences. I couldn't invoke my custom DVD templates when burning from the timeline.