By way of introduction, I became aware of this board since it has linked to some of my blog posts at Frank the Tank's Slant, so I check the board out from time to time to see the different perspectives out there regarding conference realignment. I believe that there are some intelligent posters here that understand the big picture.
One thing about NBC/Comcast: no one should assume that anything other than a Big East team hosting Notre Dame (e.g. Navy once it joins) will ever get onto the over-the-air NBC network. The Big East has a large amount of potential value to NBC Sports Network simply because of the volume of games that the conference can provide (although like the OP, I'm much more skeptical of both their ability to grow or the true willingness to spend - the newly proposed Fox sports network has much more promise as a legit ESPN competitor, IMHO). However, that doesn't really translate to over-the-air NBC, where the business model is based upon a couple of big home runs as opposed to a lot of singles that provide volume. One poster above alluded to NBC only showing figure skating on Saturday afternoons, yet everyone needs to realize the average figure skating program actually draws very good ratings at a fraction of the cost of college football. It's the same thing with the fishing shows on NBC Sports Network - those shows that are actually extremely profitable since they can be rerun all week and still draw audiences. At the same time, NBC's fall sports lineup is much more filled up than people are giving it credit for - they have a ton of golf, such as the FedEx Cup and Ryder Cup, and a new Breeders Cup deal that takes up most (if not all) of the fall weekends that NBC isn't showing Notre Dame football. Note that golf is specifically important to NBC/Comcast since they synergize it with Golf Channel (which they also own and happens to have better carriage and rights fees than NBC Sports Network), so they're not moving golf for any college football outside of a Notre Dame conflict.
To the extent that NBC/Comcast is interested in the Big East, it's 99.9% about cable. As I've said, there might be a stray exception for those years when Navy is hosting Notre Dame. That's not a knock on the Big East - sports rights fees are almost solely driven by cable right now. We've already seen the BCS bowls go to cable exclusively, the Final Four will be on cable in a few years and you'll be seeing more and more MLB and NBA playoff games end up there, too.