Hi
I had SRA for short time whilst on a LLU ADSL line.
I did work, with the sync speed fluctuating quite often without a full resync and the SNR staying pretty constant, however it didn't make the line any more stable overall or more more immune from resyncs. I guess the problem with some lines is there are times where there is more noise than a 6db margin can cope with, so it makes no difference if SRA is keeping that margin constant or not, it's going to get knocked out regardless. It was more annoying really as sync speed would drop at night, so it was trading a fluctuating SNR margin for a fluctuating sync speed, but providing no more immunity to resyncs, i.e, not providing a benefit.
G.Fast is suppose to sync back up very quickly, so SRA may be even less of a benefit.
BeThere did trial it on ADSL2+ and found nothing but problems, it never went live.
The trouble with introducing things like SRA, G.INP and vectoring after the fact, is that the horse has bolted, by that I mean there is a very broad range of modems out there, all of which have been sold not requiring to support whatever UK/Openreach flavour of these technologies they trial, so it's almost impossible to introduce changes without breaking far more than it fixes.
Regards
Phil