There my be some circumstances where an ADSL line would improve once FTTC had arrived and users started to switch.
I'd imagine a line with say 2Km of E-side and 100 yards of D-side would get better as a lot of the interference in the 2Km from cab to exchange would disappear now others ADSL signals were no longer on it while the 100m of D-side should not be too affected by VDSL cross talk impacting the ADSL signal.
Is my thinking correct you you reckon?