This is done in a way so that no station receives the results before any other. How Research International accomplishes this is by having a set time they call up all the stations. At the chosen time, Research International will have telephone operators ready to with the results to telephone all the subscribing stations at the exact same time. The results are also sent to the stations. Once the respective stations have received the results, it is out of Research International's hands until the next survey.
Stations tend to market themselves vigorously around survey.
Wellington has just been in survey and the next survey will be done in October. They also promote themselves heavily, advertising on every known medium, if the station budget permits, in the hopes to push their name and win over new listeners. Stations might up their promotional gimmicks, giving away bigger and brighter, more valuable prizes. This is all in the hope they will up their image and popularity amongst the listening audience and improve their ratings. It tends to be a rather fruitful practice accomplishing the desired outcome.