Many Industrial IoT TSCH networks, such as SmartMesh IP, operate in the same 2.4 GHz frequency band as WiFi. As the smart factory becomes more and more connected, WiFi starts being rolled out on many factory floors. It is hence completely legitimate to question whether WiFi impacts Industrial IoT TSCH networks, and in particular their end-to-end reliability. In a setup which replicates a worst case industrial setting, we conduct a thorough experimental study which looks at the performance of a 47-mote SmartMesh IP network undergoing several levels of WiFi interference. The result is that, even though the latency and power consumption of the network increase, end-to-end reliability stays at 100% even under very high WiFi interference. The conclusion is that TSCH technology at 2.4 GHz, such as SmartMesh IP, is perfectly appropriate to for an industrial environment where WiFi is heavily used. This paper is complemented by a research report which contains all the information needed to replicate the measurements, and the raw data.