What you really found is...a bug in the Geneva AFCAD!
I've checked the map, and that Parking 62, where that AI you hit the tail was parked, shouldn't have been there, it's in fact past the line of Parking 61, and that would allowed clearance for a 747. In fact, the parking position looked odd, because the AI was parked exactly over a vehicle taxi.
In fact, a "problem" with GSX, is that will force us to be way more careful when designing AFCADs in the future.
If you run the Couatl_Updater.exe from the FSX\fsdreamteam\FSX\Couatl folder (with FSX closed), it will fetch the updated LSGG AFCAD automatically.