The only CD Trump has in lockdown in Wisconsin is WI-07 (the northern part). Cruz has in lockdown the area around Oshkosh (WI-06). The rest are pretty close, although Cruz has a clear lead in WI-05, and Trump in WI-01 (Paul Ryan's CD).
Sorry, are you basing that on this poll, or just your gut feeling? This poll does have crosstab info on the congressional districts, but the sample sizes are tiny, and don't seem to line up with what you're saying (unless I'm reading them wrong).
Samples
are small, but they have the numbers on a spreadsheet for each of the eight CD's.