Classically difficult positioning environments have always called for some augmentation technology to assist the Global Positioning System (GPS). "Locata" offers augmentation, and even replacement, to GPS in such environments. However, like any other system relying on wireless technology, a Locata positioning network faces issues in the presence of RF interference (RFI). This problem magnifies due the fact that Locata operates in the licence-free 2.4GHz ISM band. WiFi devices operating in this band have been identified as the most likely potential interferer, due partially to their use of the whole ISM band. This paper evaluates the performance of Locata in the presence of WiFi interference. A comparison of Version 2 and Version 3 devices is presented. Evidently very significant advances and improvements have been made in Version 3 for rejecting RF interference (RFI). Test results presented in this paper give an insight into this situation. Also, Locata characteristics have been identified which can be exploited to mitigate RFI issues.