It didn't go through the courts because it would have lost due to the lack of evidence at the time. However, if there are now eye witness statements from former team-mates and possibly additional evidence it alters the balance somewhat.
The Sunday Times lost the Court battle on how their article should be interpreted. The High Court decided what they had written was saying Armstrong was "a fraud, a cheat and a liar". And on that basis they decided to settle out of Court and say they had not meant to accuse him of being a fraud, a cheat and a liar.. They could have gone through the subsequent Court process in which case they could potentially go for an Appeal now on the basis that Armstrong had lied in Court. But since they decided not to, and the Court case that did take place was about interpreting what the Sunday Times had written, not whether it was correct and not or whether Armstrong was indeed a fraud, a cheat and a liar, I suspect it will be very difficult for them to come back on it just as it will be for Armstrong downstream to challenge the USADA finding having decided to not challenge it now. BICBW