There is some kind of easter egg on the mansion ground for sure. If you stand where the flower delivery guys stood in the main mission and use instinct a scooter and a motorcycle light up right behind a wall ( where the limousine is/was). Also the ledge lights up meaning you can climb it. Those three thing are all that is lit up, nothing else.
When you zoom in with x3 zoom back on the roof of the safehouse the motorcycle says ‘Stallone 47x’’. That in combination with the door you can blast open must mean there is a way to get on the grounds.