I'm in the US so I'm quite alarmed by this claim. Perhaps you've remembered where you read this study? Or the city at least?
It wasn't a specific city actually, it was the National Victimisation surveys where they broke down the figures for interracial rape - I don't believe they break it down like that anymore but you can find the previous reports online.
I can't speak to the accuracy of the data (I believe it is estimated) but it certainly supports the view that studies can be used to make a particular demographic look bad which is what previous posters are saying about the trans statistics.
Presently the FBI appears to have only published the full statistical tables up to year 2008. After that the FBI website only has smaller “bulletins” that do not include the full data.
From this data we find that blacks commit sexual assault against almost as many whites as blacks. However, white on black sexual assault is an extreme rarity.
Year 2003– Rape/Sexual Assault
White on Black:0
Black on White: 20,309
Black on Black: 21,104
Year 2004– Rape/Sexual Assault
White on Black: 0
Black on White: 11,610
Black on Black: 35,330
Year 2005– Rape/Sexual Assault
White on Black : 0
Black on White: 37,460
Black on Black: 36, 620
Year 2006– Rape/Sexual Assault
White on Black: 0
Black on White: 32, 443
Black on Black: 7,705
Year 2007– Rape/Sexual Assault
White on Black: 0
Black on White: 14,092
Black on Black: 12,780
Year 2008– Rape/Sexual Assault
White on Black: 0
Black on White: 19,292
Black on Black: 34,841
Total over six conservative years:
White on Black: 0
Black on White: 135,206
Black on Black: 148,380
Average over six consecutive years:
^White on Black: 0
Black on White: 22,534
Black on Black: 24,730^