Without doing any research on this, I'm shall we say highly skeptical of this claim. I know the historical rate of homosexuality is somewhere between 2 and 4%. My almost otherworldly intelligence and intuition tell me that the rate of transgenderedness is no more than that and likely a good bit less. Which tells me that if it's "highly likely" any particular person has "shared a bathroom" with a transgender, that person is intentionally frequenting bathrooms in certain parts of town or is hallucinating.