Oppositional heeling?

Where did you hear this term- in what context?  All I can think of is using oppositional reflexes to teach a dog to heel (theory behind head halters).  Are you referring to defensive heeling (ie, defense of handler, where the dog heels backwards to defend you from the bad guy?)

 It's where one person holds a leash, attached to a second collar or harness, and one person holds the leash attached to the dog's working collar. In certain points, there is pressure applied to the second collar to teach the dog to drive into heel.

I have seen this done, on a few occasions, but I can't find anything instructional, or even the TERM, online.

 I think it's unnecessary if you establish drive using the principles of learning: acquisition of the skill - so the dog is starting out with only a few steps in drive, and that's OK), fluency (dog can perform the behavior reliably on cue), generalization (dog begins to understand that the behavior should be fluent in all scenarios), and maintenance (where variable schedules of reinforcement are used to maintain the strength of the behavior).  You certainly can use opposition reflex to train a dog to tug in the opposite direction and get rewarded for that heel in drive (not sure that artificial drive is really as stellar as reinforced natural drive) and you can train a dog to recall more efficiently by having a helper hold the dog back as the owner leaves.  It's not awful to do either, but you don't have to do it to teach either behavior. 

I agree with Anne, oppositional reflex is not drive and does not create drive.  A dog either has drive(s) or not; the handler's job is to figure out which ones are strongest naturally and use them to his or her advantage.  I've never once seen or heard of oppositional reflex referred to or used in the same way as a dog's drives (hunt, prey, defense/civil, fight, pack, etc). 

The only thing I can think of that I've seen similar to this would be the forced hold for the retrieve where pressure is applied both directions (so the dog doesn't move one way or the other to escape pressure) until the dog learns to open his mouth to escape/turn off the pressure. 

I have seen and heard of the dog pulling weight with a harness to teach more collection and power in the dog's rear, but only in the context of show, not for heeling.

 As far as I know, it's done without leash pops. I'm told it's also known as resistance heeling. I haven't found much, at all....