You actually don't even need the grey box. My mom had the same problem when she had her fibre installed. No grey box, but all her neighbours had one. Turns out there was a small square Vumatel manhole cover right in front of her wall embedded in the pavement. When they came to install they just dug up a bit of the pavement, installed a plastic sleeve into the ground running to the manhole underground and connected it up directly inside the manhole. I assume whatever happens in that grey box can also be accomplished in the manholes if it is right next to your wall in the pavement.