Someone is making a very tenuous link between the 'places of special fire hazard' (ADB) and 'high fire hazard level' (BS5839)
Some common sense is required: Somewhere of 'high fire hazard level' is quite possibly not compartmented, and as BS5839 suggests has a risk of rapid fire spread. As such a call point should be very near as you want to warn other people asap. A 'place of special fire hazard' should be compartmented off from the rest of the building, so there is little risk of it affecting anyone else quickly. We should have already applied shorter travel distances to assist the person in the plant/boiler/whatever room to escape.
... Which is why as Chris points out, there is no particular need for call points in plant rooms. So while their reasoning is wrong, the end result is correct.