Control of the local loop gives incumbent telecoms companies an enormous advantage in fixed line and data communications. Incumbents still control the cheapest technology for voice calls and for high speed internet access.
In order to counter this, Ofcom and other European regulators require that incumbents allow other operators direct access to local loops. This has also means that incumbents are required to allow these other operators to install equipment at their exchanges — to handle connections from that point on. This is called local loop unbundling.
Local loop unbundling has been slow to take off as incumbents have, unsurprisingly, dragged their feet. It is greatly strengthening the position of smaller telcos.
Carrier pre-select is a simpler and less expensive, but also less effective solution: it is a less than complete solution for voice calls, and does not solve the problem for data.