There is no "line training" as such, on LLU. It's a BT specific thing, known as DLM (Dynamic Line Management) which in theory, ups your SNR if you have an unstable line. In practice, it doesn't really account for one-off blips, and there doesn't seem to be a clear path for ISPs to get it reset.
As far as I'm aware (and I haven't been keeping up to date with LLU goings on recently, so I might be wrong), no LLU operators use any form of kit like this, so your target SNR margin will stay at whatever it is initially set at, unless you have problems, then it can be altered manually by their support staff.