I recall the SAAF used a similar technique for their Hercs and Transalls into Ondangwa (Namibia) during the height of the Namibian and Angolan conflicts.
An interesting story (which I cannot confirm) is that the Angolans would install a mobile VOR or NDB, with the same frequency and ident as the Ondangwa aid, hoping to lure any unsuspecting SAAF aircraft into Angola, only to be met by anti-aircraft fire.
Apparently, the SAAF countered by changing the ident daily, and issuing their crews with the day's 'secret' ident.
Can any ex-SAAFies confrim or deny?