It is hard to find reported examples of transgender people attacking or harassing cisgender women in public bathrooms; however, a 2016 study found that12% of transgender people had been harassed in a public bathroom within the previous year.
Thinking out loud here, but that's probably because of the odd search terms, especially if Felix has his web-search settings to give UK results first, as many of us do.
What is a "public bathroom"? Isn't this term an American custom to avoid saying "toilet" in a mixed group of people?
I have just performed two web searches for myself, using the authors' sentence as a model, one with "public bathroom" and one with "public toilet".
The first gave me results about bathroom fittings, and articles about trans people's fears in "public bathrooms".
The second gave me this on my first page of results, right up at the top.
metro.co.uk/2019/03/16/transgender-woman-18-sexually-assaulted-girl-10-morrisons-toilet-8914577/