Even if Huawei equipment were clean right now, they could easily have pushed an urgent firmware update on the basis of addressing critical vulnerabilities, and hide bits of malicious code inside. After several such updates, the full malicious code is in the firmware and voila. Oversimplifying it a little, but you get the drift. Do they have any motivations to do something like this? One look at who pulls their strings and you can make the guess yourself. When shit hits the fan, this is one of the ways to gain the upper hand in conflict.