Re #2099.and #2105
The numbers, with all of their complexities are in CS 25 Large Aircraft, Amendment 5 (US equivalent - FAR 25).
The specific requirement for a TOCWS is in CS 25.703 (Page 71), with practical guidance information in AMC 25.703 (Page 368).
Agree, these are certified design numbers and justify the adequacy of the design. However my experience would examine the regulation of the operation, including maintenance to validate these design assumptions regarding adequacy of the protective systems. There are several possibilities to be explored including failure rates of the subsystems far beyond design assumption and/or latent failures of a critical protective layer.