You will appreciate, I'm sure, that I will only advise on the basis of legislation, whether it be a Statute or a Statutory Instrument. I have access to a number of sources and the latest authority is the SI of 2002 to which I have referred you. I don't exclude Google, indeed it can very often be of assistance where other sources have failed me.In this case, Google also references that same SI and nothing later.
In these circumstances, as BT have given different information, I think that it would be reasonable to ask them whether such information is based on a particular piece of legislation and if so, which one. Alternatively, are these merely self imposed standards
Leaving our 'deal' to one side, I assume that it is important for you to know otherwise you would not have asked trhe question. Its significance from a legal point of view is:- "Tom drives his truck along a highway and the load catches on a BT cable, causing damage to the load and to the truck. I act for Tom. Do I bring his action based on their breach of Statutory Duty or (having regard to some peculiarity or other) do I base it on a simple duty of care 'having regard to......'
BT should be willing to tell you upon what basis their information is given.
I have given the basis for mine. Do they wish to correct me? I am, of course willing to be corrected, as you know.