[Corrections to the below appreciated]
Should one assume that Bell actually does any free rewiring beyond the Demark when you get Fibe?
Then there is the wire to the Remote.
And then, perhaps, the wire to the CO.
I know a situation where 3 years ago the customer switched from Acanac to Teksavvy. Before the switch the line was connected to the Remote just a few houses up the street. (To an infamous IKNS card
After the switch the line ended up connected to the CO 3 km away (as evidenced by the attenuation). The line quality was very poor, and especially the upstream SNR was barely usable -- SNRM at 6, sync rate often around 400kbps. Often DSL would lose sync (typically after midnight) and try resyncing for up to 12 hours. The inside wiring was known to be not good.
I imagine that switching to Bell Fibe would:
1. Ensure a good line from Demark to Remote
2. Ensure conection to the Remote, of course.
So, if there was poor wiring to the Remote, this trick would fix that.
Cancelling and going back to non-fiber DSL from TSI etc. would retain the good wiring to the Remote. But the "phone" line would most likely go (back) to the CO (or?) to connect to its DSLAM (whatever).
So, in the above situation, that long, noisy wire would not get fixed by this trick.
That's how I imagine it. I may be wrong.