engineers good, systems bad
My company probably books about 250 SFI visits per week with BT so I have a fair bit of experience with BT Wholesale.
The biggest problem we find is that BTs diagnostics will return "no fault in the BT network" for pretty much every fault, and BT's ONLY response to every fault is to send an SFI......even if the diags(our own and bts) clearly show its a network problem or not something an SFI can fix. This means there are way more sfi visits booked than there should be. Of course, the fact that bt charge you £120+vat if they can find any excuse to blame local equipment has nothing whatsoever to do with their insistence on an sfi visit for every fault......
And don't even get me started on their callcentre! I once had a conversation with them and asked to speak to "someone that actually knows how ADSL works and I can have a technical discussion with" and was told that "we do not have anyone like that"