This would have serious regulatory implications for Openreach if true.
I suspect the origin of this claim is double pronged.
Firstly, the "walls" that were always supposed to exist between BT and OR were ... a bit porous. Regardless of everything else, it's hard to imagine that the bosses at OR will do anything other than what benefits their sole business owner (i.e. BT).
Secondly, OR have a two tier support system. Basically the cheaper ISPs pay less to OR for the line, and in return get a slower fault response time. So any ISP that pays the higher rate (and given that BT sells reassuringly expensive contracts, especially business ones, I suspect they do) does get priority treatment when handling faults.
Thanks. That sounds encouraging. However, I'm not sure what effect the 'filtered front plate' would have on the signal, once you've gone beyond it. Perhaps that's what the engineer was referring to.
These days you'll get a 5C socket with xDSL filter plate. On the front of that you'll see two sockets - one for a phone (filtered), and one (using an 'RJ11' socket) for the router - no microfilter needed.
On the back of the filter/front plate are terminals that you can use to extend the filtered phone and unfiltered xDSL circuits anywhere you want. Typically the way to do it is use 3 pair CW1308 cable (i.e. standard phone cable), using the blue and orange pairs for the phone, and the green pair for the DSl signal - and put a combination socket (phone + rj11) socket at the other end. Unless you have a house that covers multiple postcodes, it's not going to make all that much difference to the DSL signal to extend it to another room. If you have a load of Cat5e or Cat6 network cable lying around, you can use that.
However, that part of the loft is difficult to access and is not boarded over.
What you could do, is to pre-install a suitable cable from the loft to where you want the master socket - again, use CW1308 cable. Any half capable OR tech who isn't being a complete **** should be happy to terminate the aerial fly cable into a junction box in the loft and fit the master socket at the other end.
But board the relevant parts of the loft.
Or instead of the loft, find a suitably inconspicuous point in an upstairs room for the junction box.
I've been told in the past that Sky techs are explicitly prohibited from going into lofts - H&S grounds.
By way of anecdote, a few years ago BT (may have been before OR because a (supposedly) separate outfit) were hauled up in court after one of their techs was seriously injured - broken legs and pelvis or something like that. He'd been working in the loft of a flat, and unknown to him had moved to a part that was over a stairwell - and then fell through the ceiling. With no-one around to offer assistance, he eventually ran out of strength to hold on and fell some way onto the stairs. It was expensive for BT ...
So it's understandable why some outfits will prohibit their employees going into lofts - where boarding (if there at all) will be of unknown quality (I've seen lofts "sort of" boarded with old cupboard doors and stuff like that.