IO540;
I think what Gardener is referring to is the abysmal GPS coverage at the Azores.
It can get so bad there that the NDB is the only reliable aid, GPS is often either RAIM unavailable or "GPS signal was lost ..... seconds ago"
I heard a rumour last week that all en-route NDBs and VORs will be phased out by 2018. (Note the word RUMOUR in that last sentence)