Interlaced and progressive content can exist on the same DVD, yes. Most software will place the different types of MPEGs in separate VTS. If you're not sure what that means,
multiple VTS for DVD authoring is explained on the authoring intro guide:
http://www.digitalfaq.com/guides/vid...uthor-burn.htm
This is one reason I
use Ulead DVD Workshop 2 for authoring -- it does multi VTS quite well.
It's
only $49 from B&H right now, a steal. (Use
this link if you buy it.)
If you want to see a real mess, get a live DISH Network or DirecTV stream. Not a capture of one, but the actual beamed-from-satellite stream. Working with those files takes video voodoo -- they're all kinds of messed up, with interlace and progressive mixed, 24p and 30i mixed.