Thanks, nightcrafter!
I like the discussion here, it's always good to get multiple points of view!
There are a few reasons why I don't think there are only 10 BOBs in Reach:
1. Allegedly, people have gotten one BOB on each level on Legendary; nothing happened. I expect SOME indication of success when you've gotten "all" of them.
2. The "Elite Ranger BOB" description on Bnet says "Wipe them out" not "Get one on each level".
I'm not saying, at all, that more than one BOB can spawn at a time in a level. I actually specify in Part 2 of my guide that if you want to get all 7 WC BOBs, you need to replay the level multiple times. I could explain this again and again in my videos, but ultimately I'd be wasting my viewers' time.
On the topic of Banshee BOBs: you can't jack Banshees on Exodus at all. For NA, the problem is one of speed; the NA Banshee BOB goes faster than a Falcon, so that trick where you "land" your Falcon on top, hop out, and jack the Banshee probably isn't going to work. The only way you could do that is if you knew exactly where the Banshee BOB spawns, as in within a few feet, and happened to be in its path and ready to jack it a few seconds after it spawns. It's not impossible, and I've tried it before, but it's certainly improbable. In any case, there's no way to get the Banshee BOB Pilot to "land" on a roof, so you wouldn't be able to kill it separately... it still would be interesting to see if you got the GTC challenge a few seconds after you boarded him or not.
If I get time, I might try jacking the NA BOB again. Might not be for a while though, what with HCEA and all that.
PS: Dan Miller did New Alexandria and The Package, but I don't think that he did Exodus. I don't think it's fair to say that it's all because of him that the Banshee BOBs are wonky.