That might be true for your phone system but, as Prahlad J. Purohit has already said, it is not true of every phone system!

It is certainly not true for BT lines:
http://www.sinet.bt.com/227v3p3.pdf
and I think that other network operators in the UK use the same scheme.

So Edward will have to check with his target operator(s). While he's there, he should also check on the legal & regulatory issues concerned with connecting equipment to those networks...