Researcher here, you got it right on your last paragraph. For instance this is the European Cycle that is tested:
https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Ne... As you can see it is very well defined. Other tricks that are rumored are very simple: you can see the cycle last 20 min. Just instruct the controller (ECU) to change the parameters only after 20 mins of powered state.
In any case, you must know that all those practices were very well known by United States regulators, the term "defeat device" for instance appears in regulation since at least 2007: http://www.gpo.gov/fdsys/pkg/FR-2007-02-26/pdf/E7-2667.pdf#p...
§ 86.1809–10 Prohibition of defeat devices.
(a) No new light-duty vehicle, lightduty
truck, medium-duty passenger
vehicle, or complete heavy-duty vehicle
shall be equipped with a defeat device.
(b) The Administrator may test or
require testing on any vehicle at a
designated location, using driving
cycles and conditions that may
reasonably be expected to be
encountered in normal operation and
use, for the purposes of investigating a
potential defeat device
As you can see it was known that a) defeat devices existed and b) the way to catch them was to try different, random cycles more close to real conditions. The question is, if this was a well known problem and they knew the way to test their existence (and given there were millions of cars on the street with these systems), why start the big scandal precisely now?
By the way, apart from more random, realistic cycles, upcoming European regulation introduces driving tests where the exhaust gases will be collected and compared with the lab test, and only a certain % difference will be permitted.