What are BT installing?

BT have put some markings on a pavement that I'm trying to figure out. Two white rectangles, one labeled "A.I.O" (I'm guessing this is for an all in one cabinet?) and the other one, about the same size but divided into two halves, one half with the letter "J" and the other with the letter "B".

I'm mystified by this, I originally thought it was going to be a typical two cabinets, but the AIO marking suggests not. If anyone knows what these markings mean I'd be grateful - it's got me intrigued and I can't find any similar looking markings from a google image search!

J/B will be junction box. To house the cabling and duct ends that bring connectivity to the All in One cabinet.

Likely to be EO line rearragement work, or possibly infil for those on long D-Side cables.