I said 'I think', as it would be strange that I hadn't come across this 14999 sync rate myself ( I do dabble a bit with this sort of thing). Were your ISP basing this on the 15 meg or above that is the default product ?
The engineers phone call is no magic, they just ring the FTTC SMC repair team and ask for the sync rate to be reset/recalculated. I suspect that the line would regain it's full speed it's self, if left to it's own devices, if and when the original fault has been cleared. Te phone call just speeds things up.
TBH, I'm not sure what they based it on.
One problem with FTTC technology is that it is still new enough, that not many (If any) fully understand it yet. So the information filtering back to end users is rather vague, with a lot of it probably based on assumptions & comparisons to known ADSL technology rather than fact.
This is not at all helped by the BT modem being locked down (as installed) & many/most users can't even see their connection stats.
At the time my sync speed was stuck at 14999 K, I had no access to my own stats & had to just rely on the BT Performace/Speed tester, along with rather limited ISP reports to find my stats etc.
I was told to wait for 10 days or so at a time to allow DLM to settle, which made no difference.
It appears to be reasonably common for DLM, or BT's database, or something else to cause stuck profiles / sync rates that can only be "unstuck" via an engineer's visit.
Maybe when/if FTTC becomes a self-install process, end users/ISPs will be able to request profile resets directly (or maybe ISPs will be given access to reset it directly).
In my case, my original 30+ Mb actual downloads speeds (for a full month) have never returned (sync speed must have been up to 35Mb back then).
Even with the slight improvement following the profile switch to 17a, the best I have achieved for a few months is 24Mb actual downloads. They are usually around 20Mb to 22Mb.
I am not 100% convinced that my line's "faults" were ever fully fixed, or possibly BT is currently restricting my profile due to the history of disconnections etc. in their database?
Nobody seems prepared/able to confirm why I achieved really quite good speeds right through & beyond the initial 10 day training period, yet now I achieve nowhere near those speeds.
I don't suppose you have any suggestions as to how I could get factual confirmation of the current position do you?
One engineer, who is sadly no longer an active member of a different public forum (Kitz), suspected my D-side may be suffering from a continued (possibly intermittent) HR fault, not now severe enough to cause a complete loss of connection following SOME repair works, but severe enough to be restricting my profile / sync & therefore download speeds.
My stats do now show high attenuation values, but the physical line length has never been actually confirmed, so I don't know if they are too high for its length.
Unfortunately, I have no idea what the attenuation values were when I solidly obtained decent speeds, with no noticed disconnections.
So, back to the original thread, it MAY be possible that Cyberoonie is experiencing similar issues now that his line has been "fixed".