Good points, but one must wonder what purpose is served by purchasing 200 or more phones? That is a huge red flag.
Definite red flag. If not AQ types, then drug dealers would probably want them for drug deals. Temporary links between the buyer and a seller. The dealer would probably change phones once a week while handing them out to his dealers.
Of course, the same model would work with the AQ types. That would allow the cells to remain in contact with eachother but not long enough to be tracked. They would still have to meet ocassionally to exchange the new numbers (like at a local coffee shop).
So, one solution could be to record all calls from pre-paid phones. There may be millions of them, but this way, once you find a guy, you can trace back thru all his calls. Of course, you should also be tagging all intercepted cell calls with the relative gps information gathered from the cell towers. That way, once you have identified one phone, it may lead you to many others.