I'm not totally convinced about this. If you look on the Garmin website, the
data sheet for the Aera 500 shows WAAS capability. EGNOS is not mentioned.
Searching on Garmin's website, some of the very high end units show WAAS/EGNOS, but none of the lower end units show dual capability. I find it hard to believe that if the lower end units like the Aera had EGNOS as well as WAAS capability, Garmin wouldn't ensure that was listed on their various brochures and spec sheets.
(Turning on my own Aera 500, sat here in Buckinghamshire, it also doesn't show any satellite numbers above 31).
G