This article discusses how high-level executives and many top engineers might have no idea what is happening:
https://financialcryptography.com/mt/archives/001431.html
Excerpt: "How is this apparent contradiction possible? It is generally done via secret arrangements not with the company, but with the employees. The company does not provide back-door access, but the people do. The trick is to place people with excellent tech skills and dual loyalties into strategic locations in the company. These 'assets' will then execute the work required in secret, and spare the company and most all of their workmates the embarrassment. ..."
In a discussion of this article (on a cryptography list) I observed this incredulous response: "Hmm. So what does that mean a team of ex-military/intelligence security
people work there way up or get assistance with contacts and references,
replace all the key people in a companies inner security department and
start coding up backdoors, APIs and allowing VPN access to it? All without
telling anyone or getting noticed by ops people etc."
To which the other party retorted: "Been there. They are noticed, but you get orders from on high to shut up and not notice."
If that's all true, then it sounds like only a very few engineers and managers acting as moles will have specific knowledge of the program. A few non-mole engineers will sense that something's afoot, but they'll stay mum. Maybe that's as far as it goes.