Bump.
It’s nothing really to do with BT , given that it’s Openreach that are responsible for the external network infrastructure, but I suspect it’s not Openreach markings either , I think those markings were made by an Alt Net using PIA ( physical infrastructure access ) and probably indicate a blocked duct , and the measurements from the box to where they suspect the blockage or blockages to be.
No, anyway OR use grey paint when marking up, what possible benefit would there be ,marking on the pavement the distance to the cab from a random jointbox, plus OR employees wouldn’t use ‘BT’ , because it’s nothing to do with BT , civils contractors or Alt Net employees on the other hand tend to incorrectly refer to OR as BT .
TBH nobody here will know & to be blunt it's really none of your busines seither