EGPWS is a back up system. Terrain awareness/altitude awareness is a basic of instrument flying. MEA/MOCA/MSA/Grid MORA. If you're not on a printed line (MEA/SID/STAR altitude restrictions) it's up to the crew to decide if MSA protection is provided(ie above MSA for the portion of the MSA circle that you're in). If MEA or MSA protection isn't guaranteed, and basic terrain awareness isn't available(terrain chart/minimum radar vectoring chart), then you need to operate above the grid MORA.
Yes, the system, because of the backup safety system, worked. It's not supposed to rely on the backup system. There's a reason why a EGPWS alert is usually a mandatory reporting event, because it's not supposed to happen in the first place.