To my understanding, for the elders to proceed to contact WT legal dept for direction on what to do, there needs to be 2 witnesses to the same act, OR at least 2 separate acts involving 2 separate victims who each accuse the same person, OR there needs to be an admission from the accused.
If only one victim makes an accusation against another JW, the elder's 'investigation' likely amounts to meeting with the accused and asking if he/she did the thing they are being accused of doing. If the answer is 'No', then the matter is dropped and the accuser is warned not to mention it further.