I've never seen a CBT mounted that way - have you? Normally they are underground or on top of a pole, to avoid tampering.
Many, and at different ends of the UK too - from council-built flats, to terraced commercial street, to large houses subdivided into flats. In most cases near an old copper DP - which may be my answer in this case, if the DP remains underground which is likely. I can see individual cables to footway box CBT making sense for a 2-3 flat conversion, but 6 is a large number and I'm pretty sure I've seen 4 port CBTs on commercial terraces.